My mum knows H may be there and she says she's fine. I was thinking it was a shame Mum will be there but it could be good cos H will see she has no malice towards him.
Yes, I think you are right about this ^^^^^^^. I was quite pleasantly surprised that my sister had e-mailed XH earlier this week without telling me about it, but I see that as a sign that she has begun to accept him in my life more and more. She has been speaking in more favorable terms about him recently. This is important in reconnection. My sister told me that she wrote to XH that she is sorry his mother was given 6 months or less to live and wrote to him about how difficult it is to lose a parent (our mother passed away 5 years ago).......... so her letter was more than just 2 lines. I think this sends an important signal to them that they could be accepted back into our families again.
Did your H have a good R with your mother? If so, spending time with her could be a positive.