We've just been through this and I'm sure others will also have advice.
It is best to start with commuting back into London, assuming you are. If you can walk to work from a terminus then great, but whatever you do, don't have a commute that involves half an hour on the tube once you get to London.
Once you've chosen where you want to arrive in London, find the stations that have a decent commute in terms of time, train frequency and getting a seat. This will rule out almost everywhere.
Then you need to see whether you can get a parking space at the station. If not, you need to live within cycling distance.
Then definitely look at secondary schools and I'd want to live within catchment for a good school, rather than in a place with a lot of choice. You'll want to rule out areas with grammars unless you are confident your kids will get in.
Think about primary schools last...
And don't end up with a tiny search area because it'll make finding a house you like impossible. We ended up searching in 4 villages and that worked well...