I hope I don't get shot for saying this (and I do really understand just how worrying it must be to lose the benefits - especially when I know how hard it is to get them restored at a later date) ... but ...
... surely the point of means-tested benefits is to be a safety-net from 'society', for people who have no other means of support.
If you become able, whether through an inheritance, lottery win or any other windfall, to support yourself for a period of time then surely it is actually wrong to expect to be able to continue to receive the means-tested element of an benefit income?