'Misappropriation', in this context, might constitute a section 1 Theft Act 1968 offence - where X without lawful authority treats the property of Y as X's own, with intent permanently to deprive Y.

It might also be a Tort (Civil law offence) - Unlawful Interference with Goods pursuant to provisions of the Torts (Interference with Goods) Act 1977.

In my opinio (for what it is worth) I think the lex fori for Probate would be England, as the forum conveniens.

I think, Nemesis, you need expert Legal advice, here.

Hope this helps. Bryn Pugh (BA [Law] LL.M.)