I had a chat with the Hamilton school administrator a while back, as we were looking for a house and trying to unpick how the whole admissions process worked. Basically in this area, the primary catchments don't generally overlap, so if you put your specific address in their postcode checker, it will return one school which is your catchment school.
The school will allocate first to children in catchment, and then siblings out of catchment, and after that any spare places can be allocated to people out of catchment with no sibling at the school.
From what I can tell, the norm is for schools to allocate those remaining places based on distance. So living very near the school but just out of catchment would put you nearer the top of the list. However, at that time (and bear in mind it was a couple of years ago and things may have changed), Hamilton were using a different system, whereby they didn't take distance into account, but just did a random allocation of the available places to the out-of-catchment applicants.
I think you really need to find out what system they are operating now, and what they expect to be doing in the year you apply, because it would potentially make a big difference if you are really close to the school.
It might also be worth finding out how they have allocated their places in past couple of years (this info is all available on the Bucks CC website), and how many spaces have been offered to out-of-catchment children. Obviously there's no guarantee that the same will happen in future, but it might give you a feel for how heavily subscribed they are from within catchment.
I'm afraid I can't offer any info about Disraeli. But if you don't think it's for you, then it may be worth looking a bit further afield. I have friends in central Wycombe who haven't been happy with their catchment schools but have found places in the surrounding villages such as Prestwood, Hazlemere and Holmer Green. Though I do understand the difficulty if you don't drive. (We have one car which DH drives to work, so I have a complex arrangement of taxis, buses and trains for my half of the commute/school/nursery run.)
I also have a few friends whose children go to the C of E school in High Wycombe, and they are all very positive about it. I don't believe it has a catchment area as such. Church attendance counts in the admissions criteria, but I think they also take people from different faiths, and non-churchgoers. It might not be your thing at all, of course!
At this point I would really advise doing your homework on how the admissions process works. (And specifically in Bucks, as different LEAs have different ways of working.) In particular, what will happen if you don't get your first choice school, and what the procedure will be if you go into further rounds of allocations and waiting lists. It may help to avoid some of the stress if you know what to expect.
Good luck!