I don't know that it will make a lot of difference. The school have already said that maybe she could be put up a year. I don't see the point as she would still not be challenged academically and she would move out of a group in which she does have friends. She is probably mildy dyspraxic too(?) and her organisational skills are not that great. Difficult. I would like her to be subject accelerated in at least some subjects. Total acceleration is very rare in the UK. Maybe if it was more normal we would consider it.
I can't say that grade acceleration is common where I live either but I think that some of that is b/c parents aren't aware that it is an option. I did kind of get the impression that some of our local schools could be pushed into agreeing to a skip that they didn't support based on some of what the GT coordinator at dd12's school last year said.
I did want to address your comment about it not being a way to fix the educational misfit, though. I don't think that grade skips are ever a total panacea. For my dd12 she was still many, many grades ahead of her placement in a number of subjects but it was still better than nothing. In one subject, it was the right placement and met her needs well. My dd was also dx with SPD and dyspraxia at age 7, although I'm not really sure that she has either. I think that she is just a slower more meticulous person who is very cautious. We've done better trying to accommodate and encourage the speed and give somewhat more appropriate academics.
The set group of friends in her grade is the only thing that you mention that makes me think moving her up a grade might be harder for her than my dd. My dd was already on her 3rd elementary school by the time she skipped the last year of elementary so she wasn't married to staying with friends she had known forever.