"There are limits - at least in most denominations - as to what is to be believed."

Who says? And where do they derive the authority to determine what those limits are?

"On the whole the 7 Ecumenical councils are a good start.."

There's been a lot more than seven. What I'd like to know is at point exactly did the entire Church slip into universal apostasy? Was it in the fourth century? The eleventh century perhaps? Protestantism asserts that somewhere along the line the Church began teaching apostasy. When exactly was that? You can't just say that the Church fell away after the apostles just because there's been a whole lot of sinners in the Church who have done immoral things, because what else is there? Why would you expect perfection from imperfect and flawed souls? Even St. Peter denied the Lord. Imagine that, the first pope denied even knowing Jesus. That shouldn't exactly bode well going forward, and so it shouldn't be that surprising if there's been some bad popes (Alexander V, Innocent IV...etc.), some bad clergy, and some improper statements issued in "official documents." Church documents are not infallible. Not everything everyone who is Catholic has ever said is automatically regarded as infallible, nor is everything every Catholic ever did automatically good and righteous. Why do you assume such?

You talk about the "local" church. Which "local" church? In my area, you can travel five miles down the road and find a Methodist church, a Pentecostal church, a Baptist church, an Episcopalian church, a Catholic church, and even a "church of Jesus Christ Scientist." There's also a Jewish synagogue in there as well. What "local church" do I take the matter to then? Why should there be this confusion?

It doesn't have to only be to the bishops. You can even go talk to lay individuals in the Church if you want to, but Christ did establish a priesthood in the Apostles and breathed the Holy Spirit into them (John 20:22) and said "Receive the Holy Spirit, those sins you forgive are forgiven and those sins you retain are retained." What happened was, as is recorded in the book of Acts, the Apostles appointed successors and breathed the Holy Spirit into them, calling them "bishops," and this has been going on from one generation to another for the past 2000 years. Also as recorded in the book of Acts, the masses got too numerous for the Apostles and their successors to manage, so they franchised out and divided up the labor, anointing and breathing upon presbyters (priests) and deacons to service the masses when they couldn't be present. Thus, a very clear hierarchy within the Church was established early on and is still in effect to this day. It's only among the schismatic groups that this continuity was broken (along with the gift of the Holy Spirit given to the Apostles by Christ).

There's numerous scriptural proofs for the organizational structure that existed within the early Church that I could get into, but I'm certain you understand that "Church" doesn't mean just the "building" itself. "Church" is the Body of Christ, of which all people in all church buildings are members of, whether they be big or small buildings, private houses or public spaces, catacombs or basilicas. Each time St. Paul wrote to the individual congregations he wrote in a style: "to the Church which is in Corinth" or "to the Church which is in Ephesus"...etc. He didn't say "the Corinthian Church" or "The Ephesian Church" or "The Southern Baptist Church." Note also that Paul and James always deferred to the determination of Peter. "All the believers were one in heart and mind" (Acts 4:32). Now tell me, are the Calvinists really of one mind with the Lutherans? Are the Evangelicals really of one mind with the Unitarians? It seems the only way to have a universal church is the have a church that actually existed everywhere and at all times. What other church besides that Catholic Church can make that claim? It's right there in the lines of succession.

"Certainly the belief that a piece of magic - being baptised as a baby into heaven is deeply flawed..."

As a protestant, I used to believe this, which is why I never got baptized all those years, ignoring the words of Christ who said: "Unless you be born again of water and the Spirit they can not enter the Kingdom of God" (John 3:5). The reason I didn't know this is because I was a Protestant, and I believed that I didn't need to read the Bible, because I had "faith alone apart from works". My theology was "oh yeah, I believe in Jesus, so I can do whatever I want and God will account to me the righteousness of Christ as substitutionary atonement for all my sins past, present, and future." You can imagine the shock when I started actually reading the Bible and discovered James 2:24 (and pretty everything else in James)... "You see that a person is justified by works and not by faith alone." ... I remember having an argument with James when reading this the first time.

"as is the idea that a brown scapular will do it:"

The brown scapular devotion is just a private devotion, and something the Church considers "worthy of belief." It's not required of anyone and certainly is not a means of salvation [apart] from Christ. That is, if a person is indeed saved by devout use of a brown scapular, it is not the "power of the scapular" that is doing the saving, but the power of Christ working through it. It does help some people to live holy lives and serves as a reminder to many of their daily consecration to Christ at all times. Why should it be so hard to believe that God works through his creation, or that God often uses created things to help aid in the salvation of his creatures? For example, he fed Elijah in the desert "through" the crows (1st Kings 17).

If you're hung up about the devotion to what the Church calls "sacramentals" such as a brown scapular, just look to Acts 19:11..."God did extraordinary miracles through Paul, so that even handkerchiefs and aprons that had touched him were taken to the sick, and their illnesses were cured and the evil spirits left them."

If that wasn't recorded in Scripture, a modern Protestant would clearly determine such to be a form of idolatry or witchcraft. "How can Paul's handkerchief cure the sick?! Only Christ can do that!" The point though is that Christ was the one doing it. Christ didn't abandon His Church when he ascended back to the Father. He lives through it and these miracles and devotions are signs of His continued salvific presence in it. I don't see how any of this is "deeply flawed."

"There's no point in claiming the modern catechism says something which that the 'infallible statement' explicitly denies."

All this is akin to the statement "There is no salvation outside the Church" which the Church has tried to explain numerous times ever since it was declared. The problem is the limits of language. When a Protestant says "There is no salvation apart from Christ" nobody bats an eye. When a Catholic, understanding that the "Church" is indeed the "Body of Christ," says that there's no salvation apart from being incorporated into the "Body of Christ" (and all that entails) suddenly it's this controversial and exclusionary thing. The fact of the matter is, Protestants ignore the fact that the Church vigorously condemned "Feeneyism" (that one has to be a member of the Roman Catholic Church specifically to be saved). It's heresy actually.

The reason I bring that up is that what you consider to be "explicit denial" is not actually "explicit denial." The fact of the matter is, for the faithful, the belief in the assumption of the Blessed Mother is essential for Christian unity, and to go against it makes one no different than any heretic from Pelagius to Arius to Nestorius to Luther and even Fr. Feeney (although I think he recanted his position). What I find funny is that Protestants (who reject the authority of the Church post-Trent) end up being strange bedfellows with Sedevancantists (who reject the authority of the Church post-Vatican II), and it just all goes to show that people have found something or other to complain about for eons. After the doctrine of the Trinity was established, I'm sure the Arians were upset too and had their own conclave to complain about "Church abuses" too. It never ends. It's all the same. Satan never changes his tactics.

"But for an outsider to join an organisation based on spin, lies, hypocrisy and a propensity to persecute other Christians that still persists, shows a depressing lack of discernment..."

Well that should certainly put one off of being an Evangelical fundamentalist then...