Pension - how much can you have in the bank?

My father-in-law has a few pounds saved, not a lot. He wants to make sure he has a good send off (I know it's a bit morbid but it's what he wants). Anyway, he's now worried that he is aculating too much. Does anyone know how much he is allowed to have in the bank before the pensions/tax man starts taking it off him? Thanks!