Hi there, I was brought up in Marlow, but now live about 20 mins away, - so my understanding of the schools is out of date so I didn't respond to your post initially, but I'll give you what I know!
It was always Spinfield and Danesfield that were the two best schools - and it seems to be that they are still are. I was in catchment for both, but I went to Danesfield. If I was to move back, i'd definitely go for either of those if I could.
Holy Trinity (Holy Bog we used to call it) is outstanding now, I have a friend who's children go there and she seems pleased, they came from Little Marlow infant school which is lovely.
St Peters - Catholic, I don't know anything about this school I'm afraid.
Burford - Marlow Bottom - my nieces went here until recently, it's a good/ok school, getting better I hear.
Foxes Piece - this was (i'm sorry to say, and my knowledge might be out of date) always the school in Marlow to avoid. It's obviously got a lot better as it's now a 'good' rating - it was a requires improvement in 2016. I had friends who moved to avoid the school and others that sent their children there, and it wasn't wonderful... but I am quite prepared to be shot down, as my info is about 5 years out of date.
Hope that helps! Good luck.