I installed solar thermal myself having been on a course with Tony Stone of Solar Savings at Wisbech, system is 2 x 20 Evacuated Tubes mounted on East & West roof side which gives hot water from april to sept end and warmish at other times.
I then asked Eco2Solar to install Solar PV onto my Roof and workshop roof , 2.94 KW in total which went live on April 16th 2010 and this outperformed the estimated generated figure by 56 units coming in at 2506 KW for the 12 mths. earning us nearly £1100

married live in bungalow, with South facing rear roof, which I completely refurbished in 2009 including under floor, internal walls and extra ceiling insulation. went to all electric heating using electric boiler which does eat power in winter but still " no gas bills"

Make sure you understand the technology and how installing it affects your roof, some sales people don,t bother to explain the impact it may have. Get several quotes and ask for references, Ive only been asked once by my installer for a reference but know they are busy, I have given advice to others who have asked.

Beware signing up for free installation remember they are there for years will you be? selling your home may be difficult if you do not own the right to the Feed in Tariff. My No 1 tip would be Get in Now whilst Feed in Tariff is guaranteed.