Cambridge is one of the most expensive cities for housing. As has been said above, Bedford is less so (but, because it's easily accessible from London, not particularly cheap). Bedford is quite pleasant, even if there is rather too much 1960s concrete in much of the town centre.
I've never really warmed to Colchester; it seems a bit soulless to me. (Chelmsford might be a better prospect for you, although you'd need to check on house prices there).
Bishops Stortford is rather pleasant, and has Stansted Airport on its doorstep, with fast access to London, but those factors add to housing prices.
Ipswich (just down the road from me) is a very 'up and coming', with a rapidly developing waterfront area (with loads of nice restaurants and bars) and generally quite pleasant, with loads of parks and green spaces. It's an hour's drive from Stansted (with a bus service there every two hours as well), about 70 minutes by train from London (although there are plans to cut that to 60 minutes). Employment opportunities are reasonably good, with BT's national research centre on the edge of town and many insurance companies having their HQs there. House prices aren't too bad either.