sorry to hear your loss fella, we went through this few years back when dad passed away.. he had a really crap financial advisor that didnt know sh*t and confused mum.
in the end i got all his funds, pension bits and bobs, and sat down one day and just called them all up and did it myself. it’s not a nice thing to have to do but mum was at her whits end. make sure you have a good few copies of the death certificate because they won’t do anything without that and get used to writing lots of letters.
the council tax was cut for mum, i called up and hassled them i think she got a one person allowance.
the worst part is still getting letters sent to dad 2 years later, just brings it all back for her. the pension is b*llshit though, she only gets half of it after he worked his b*llox off since he was 15.
best of luck, it gets easier the twins will help loads for your mum, luckily dad saw my nephew about a month before he passed away.