BluePenguin, if it were me and I really couldn't move house (and I'd change jobs and downsize if need be); then I would first check out all I could about the school. Get insider info, maybe even post on here asking about the school - get existing parents' thoughts, even teachers'. For instance it might be broadly known that it's going to be an academy or there is a new, forward thinking head - if it's at 19% then something must be happening there.
Definitely look round on the open days when the pupils are in.
I would also consider how many other like-minded parents there are like you with children starting.
Sometimes new housing and changing catchments change a school demographic - this is what is likely to happen to my brother's closest secondary school, not so great at the minute, but they live on one of two large, pricey new-built estates & there are no nearby private schools, so eventually those estates will feed into the secondary school.
Then if it still looked bad, appeal? Give the school a chance for a term or two then private ed? Home ed?
What do you think you should do?