another vote for Milton Keynes - good rail service into london - 30mins fast, 1hour during peak times - and hopefully going to get better as the railways (network rail?) are moving their HQ here soon so hopefully they will make sure they get a good service for themselves 
very easy life for families, lots of things to do, plenty of parks, libraries, skate parks and free stuff as well as paying stuff like the indoor ski-ing, indoor sky diving, ice skating, bowling, swimming etc. local football team is very community orientated and runs very cheap holiday courses if kids are into footie
schools - bit of a mixture but there are some great ones around
loads of shops - massive supermarkets, big ikea, shopping centre with John Lewis, M&S, Debenhams, TKMaxx and all the usual high street stuff, plus plenty of little local shops
traffic is easy, some people are scared of the roundabouts but it makes driving around the city very fast usually, keeps cars away from pedestrians and if you make a mistake you know you can turn around at the next roundabout which you will be at shortly instead of panic-ing about where to go next.
areas between the main roads that divide the place up tend to be known as grid squares - all like little self contained villages, some are new and still being built, others have been around since the doomsday book, most seem to have a local community feel and things going on.