Hello Keri,
I would say that gut feelings should be the first thing you should trust! Anyway, I would suggest visiting other schools just to have some terms of comparison if you don't have children at school already.
You may check the data dashboard on the Ofsted website to check the school performance if you want something quantitative.
Like I said, we live quite far from Clapham Manor, and I was just looking at options to fill the last two places on the application form for the sake of saying that I had not left any gaps - our first four choices were reasonable in terms of distance/offers made in the past, but for the remaining two we could as well have put down schools in North London
Anyway, we are hoping to get into Alderbrook as we are really happy with the nursery there. It is the closest one to us, and definitely worth a visit if you are considering SW12 as a place to move to. If, on the other hand, you are definitely planning to stick with SW4, I guess Wix could be an option for you. Off Abbeville Road you have Bonneville. Not sure what you can find past Clapham North, or what the situation is like re faith schools close to SW4.
Good luck!