I live in MK and love it - it's very family friendly and you can get a decent 3 bed house for that. Plus if your dh wants to get to Islington it's easy to get to from Euston by tube or bus.
I've posted before about why I like living here - so rather than type it out again, I've just copied and pasted from a couple of earlier posts. But shout if you have any questions and I'll do my best to answer them.
We live in Milton Keynes and it's fantastic for families.
Lots going on, nice houses, train takes between 30 mins and an hour to Euston, some great schools (albeit also some to avoid), loads of parks and countryside integrated into the town, decent shops, big cinemas, good theatre, fabulous arts festival every other year (it's this year, woohoo), lots of sports and clubs and stuff to do for kids and adults, easy to drive around, definitely worth checking out.
Schools - think you can apply for the Bucks grammar schools (people go to them in both Buckingham and Aylesbury) but in MK there are some schools with good reputations. ds1 is at a fab junior school that regularly wins national awards for all sorts of different things they do, and most importantly he loves going there and seems to be thriving. It feeds into 2 good senior schools. ds2 is at a decent infant school, again, really enjoys it and has some nice staff, they've really helped with some stuff he's struggled with and he'll move on to the same junior school as ds1 in 18 months time.
Houses - have just had a quick look on rightmove for 4 bed detatched houses under £375K (on the basis that you can negotiate down!), not sure if you want brand new first ownership of a house or a new home that's up to 5/10 years old rather than 100 years old, but even at £300k there are plenty in decent areas. There are some nice older towns around - Stony Stratford, Newport Pagnell, Olney, for example, but lots of the grid squares within MK itself are based on old existing villages so you have the best of both worlds. Where I live, I live opposite a park, have 2 more within 5 minutes walk, the station is a few minutes walk away, there's an old village green, a Norman church, things like toddlers groups and the WI locally - and yet 5 mins in the car and I can be in John Lewis and the shopping centre or Sainsburys (underground car park handy when it rains!), Morrisons, Asda, Aldi, Lidl, Sainsburys/Tesco locals, and within 10 mins there's big Tescos x2, Costco, Waitrose, Ikea, Primark, loads of M&S, and more.
Lots of beautiful countryside within easy reach (often walking reach) of houses
Easy to drive around
Good links to london by rail and road
Fab cultural scene
Plenty of shops
Lots of national trust type places, museums, etc around to visit
Plenty of stuff for kids to do
Some decent schools and some great ones
Best of both worlds in that some of the old villages are incorporated into the city so you have the grid squares that are all self contained square 'villages' that have their own things going on
We moved from central London (having been there for about 20 years) and although we miss it in some respects, we do enjoy living here - and have a much higher quality of life than we would have done in London, now we have dc.