Money-spinning schemes to torture the bereaved

Dad had shares - not many, but a few and in his will he explicitly left them to mum, funnily enough. I rang his investment company to close his account and transfer his shares to mum. They asked for a copy of his death certificate. I thought, naively, it'd be that easy. They then sent a letter saying they could not legally proceed without a letter of probate. I checked with a lawyer who said this would cost £200. I rang the investment company again to say I had his will which stated mum was to get his shares. Apparently his will, in all its explicitness is not a legal enough document! They want to force her to have to make appointments with lawyers and pay upfront for a letter to get what is already legally hers. When they are thinking up these money-spinning schemes, do they never stop to consider the vulnerable people left behind? They should team up with Sheila! I have submitted a formal complaint, for all the good it will do me.