Factor, just because there is no will does not mean the wife inherits everything. Generally speaking she would inherit all personal possessions and the first £250,000 of the estate with the rest going to other beneficiaries, presumably including the OP, though she would retain the right to live in the house during her lifetime.
My interpretation of the situation is that OP inherited a chunk of the house but the wife could not be forced to moved out so OP decided to leave her to it and wait it out. Now that wife is gone, OP has found out that the house was in fact rented out, so wants a fair share of the rent received but doesn't want to be implicated in any wrongdoing.
This is very complex and I would imagine proper legal advice is definitely the way forward.