Hey Jonathan, I'm just catching up on this thread. Sorry to hear the news about your mum, but like TD said, you really were lucky to have the opportunity to be there & to say what you needed to say. My mum died last September on the other side of the world. The legal crap will no doubt be a pain in the arse, but further down the track I expect that it will be largely forgotten, & importantly what will remain will be the fact that you were able to reach 'closure' with your mum.
The detached feeling you described is perfectly normal, as are a huge range of responses, everyone is different, & there is no right or wrong way to be or to feel at this time.
All the best
Cuppa & MrsTea.