I have a child at the school too and am really happy with it. It's a really caring and family orientated school. Kids are really well behaved. KS2 results are really good (actually on a par with other schools that are better thought of in the area, for example St Polycarps). KS1 results are not quite as good yet but they've moved the really good KS2 Leader to KS1 so I expect the results there will be excellent soon too. The school also has a new Early Years Leader who is very good, comes from an Outstanding school and is making lots of changes. The new Head is really good too, very keen, has very high aspirations for the school and keen to listen to views of parents and make changes.
Don't be put off by the last Ofsted report. It was done when the criteria had just changed, when the school were in a really disruptive phase of the building works, and when they had an interim head teacher. Things have changed a lot since then and the feeling at the time was that it was an incredibly harsh view of the school.
As to your question as to why some parents avoid St Peters... I think it's down to snobbery. Yes, St Peter's does have a more mixed catchment compared to some other local schools that exist in upper middle class bubbles. The parents at St Peter's are mostly middle class but there are some families from the less well off parts of Wrecclesham. However, the mix of kids means that they all learn to get on with people whatever their background - this is one of the reasons that we chose the school and why the head of Weydon apparently really likes kids from St Peter's (because they mix well - apparently the Head Girl and Boy at Weydon are very often ex-St Peter's pupils).
If you're stuck on South Farnham, then you might be in luck as they are apparently taking 3 classes this year (or so I heard on the rumour mill).
Apologies for the essay, didn't mean to write so much.
p.s. There's an open evening on the 19th Nov if you want to have a look round.