I have considered a wind turbine... there are plans for DIY ones which
don't cost too much. I have also been thinking about direct drive heat
producing ones, ie: convert the kinetic energy into heat using a heat
pump or stirling engine rather than into electricity first. This would
remove the efficiency loss of converting to electricity and also
produce something like 2-3 times more heat that the kinetic energy
taken to drive it.

Solar thermal however, I think should be exploited first as it seems
to yield the big numbers for something as simple as heating air. I
worked out at the weekend that I have enough space for an 8 square
meter freestanding collector on the south side of my house. Hopefully
enough to average 1.6kw during daylight hours during the winter.

BTW: you can get sizeable grants for solar/wind/hydro projects (yes,
even on a domestic scale). The only downside is that you must have an
approved system (not homemade!) and it must be installed by an
approved installer who will cheerfully jack up his labour cost to eat
up your grant. I know this because I got a quote to have solar matting
installed for my pool and the guy wanted to charge me 1000 quid for a
10 hour job. :-(

Regards

Nick.