Two possible leads for you:
1. Speak to the people at Twinwoods who have restored a derelict tower to excellent standards. It IS cold in there despite new radiators, but they have kept the original windows - double glazing would be a must for making it a house. Link:
http://www.twinwoodevents.com/
Twinwoods is signposted off the road just North of Clapham, itself North of Bedford. Coming from the North you'll need to come off the A6 before the new bypass section, following signs to Clapham.
2. Somebody converted the RAF Podington control tower to a home, and it looks pretty damn good. Not far from Twinwoods so you could visit both on the same trip.
Podington is best found by following signs for Santa Pod raceway, you'll see these further North on the A6 between Rushden and Clapham. The lane down to the raceway passes a memorial, then a riding centre on the left. Keep going past the main entrance for the raceway and the control tower will soon appear in front of you. Sorry, don't have any contact details for the owner.