First, don't worry.

I am assuming you are not and have not done anything illegal.

If the police consider it worth following up, you will hear from them. If you do, then tell them nothing beyond stating that you don't know what they are talking about (or words to that effect).

If they come to your house and want to come in "for a chat", refuse to answer any questions. (A tape recorder might be an idea to record what they say, but you keep schtum). If they insist on questioning you, make sure this is done at the station under caution with your solicitor present. His/her advice will probably to stick to "no comment", with which I agree. Unless you are arrested, you are under no obligation to be interrogated at all.

If they turn up with a search warrant, they have to state what they are looking for and be able to show a reasonable cause for expecting to find it.

Find a good solicitor (one who knows about this sort of thing, not just any old bod) now, and tell him what happened.

It might also be an idea to speak to the nephew in question; it's possible he will be visited by the police and he needs to be prepared (he might like to get a solicitor as well if he hasn't got one).

All the best.

LeX