Okay, I'll try to summarise my dillema.
DD1 of 3 is at our local school. It's great, we love it, very inspirational head but it's probably changing from a 60 - 90 intake which will cause a bit of disruption and make it a different school I think. We own a great house and could afford a bit more in that area in a few years, hopefully. The secondary is mediocre at best and has had problems with bullying in the (recent) past.
There is an outstanding secondary a few miles away. It's been outstanding for over a decade and we really like the ethos and feel of the school. There is no way that DCs would get in from where we are and even if they did it would be a nightmare getting across the city.
We could afford to rent a reasonable size house in the area with a good secondary, could never afford to buy. Not sure about the primaries but sure that we'd be happy with one of the 4 that would be in catchment for the secondary. If we move DD at the end of Year 1 we'd move in time to apply for DD2s place.
If we move just before we apply for DD1s secondary place then we would have at least four years of ferrying the younger ones to the old primary and DD1 wouldn't know as many people. If we move now though, we're probably committing to renting for a good few years and might not feel settled at all.
Sorry,this might not make any sense to anyone else but thoughts would be very much appreciated.