Has anybody suggested Milton Keynes yet? (sorry, haven't had time to read entire thread).
We moved here out of London 9 years ago and love it. I know it has a bad reputation amongst people that don't know it but it's a fantastic place to live. I think of it as the town that can't decide if it's a city or a village...
It has all the benefits of living in a big city - big shopping centres, big supermarkets (at least one mega sized version of each of the big 5 plus aldi, lidl, costco), fantastic theatre, some good restaurants both independent and chains, a decent train link to Euston (between 30 mins and 1 hour depending on whether you get on a fast train, a medium train or one that stops at every station along the way!), history (really - right from the Romans, but most famously currently for Bletchley Park, home of the code breakers and birthplace of computing), sport (lots of different sports to play and watch, National Badminton Centre and National Gymnastics centres are here, the MK Dons have an amazing stadium that lots of other sports and teams use too - the Rugby World cup is holding some matches here, and they also have a very strong educational arm that is very involved with the community, Red Bull F1 are based here and Silverstone is just down the road), skating rink, athletics is strong (even have a gold postbox for MK's own olympic gold medallist), loads of parks with a strong Parks Trust that organise lots of different events - from walks and wildlife spotting to fairs (I could be at the May Day fair right now), music events, open air cinema, festivals and more. There's also an award winning International Festival every other year in July with lots going on. The OU also has its HQ here, along with several other big companies. And the cinema companies have chosen MK to launch their first UK 4-d (seat shaking/etc) cinema and some other whizzy type of cinema that's a first for the uk too.
It doesn't have a single 'main high street' - but that's because it has lot of them... They've used a gridded road system so each grid square has its own set up. Some are based on ancient villages that MK was built around (for example, mine has a church going back to the 1100s, a reasonable village pub, and a good sports and social club, nice playgrounds, several parks, small village shop and is a couple of minutes walk from the station, a junior and infant school - there are a choice of a couple of good comprehensives in the next squares over. Others have different characters - some have a cricket ground or football club, some have bigger high streets within them, lots of places have nice little shops or coffee shops or bars, loads of playgrounds spread around and so on) - so it feels much more like a collection of villages than just one big amorphous town. There also seems to be lots of stuff going on - art classes, dog walking, ski-ing (indoor snow covered ski slope),
There are also redways which are special designated pathways that connect all different parts of MK which mean that you can walk or cycle across the town without the need to negotiate the traffic - they're mostly through parks - which is a really big bonus if you like walking, running, cycling etc. The roundabouts are much maligned but actually make life driving around much easier and less stressful than driving in other towns I've driven in - not least because if you make a wrong turn and you're on a grid road, all you have to do is go up to the next roundabout and come back again. Despite having driven in London for years, I had to drive in Oxford recently and it reminded me what a nightmare driving could be when you have narrow roads, parked cars on the sides, pedestrians and cyclists popping out, and so on.
Schools are a bit of a mixture but there are some fantastic ones if you choose the right place to live.
It's the fastest growing place in the uk and the fast growing job market if you decide you want to work locally.
And house prices - £350K should get you a nice 3-4 bed house within decent striking distance of the station, with plenty of parks around and be pretty nice...
Shout if you have had your curiosity piqued and have any more questions!