There are 2 options to the scheme.
1) Rent a roof - this is where a company keeps ownership of the panels and you get free day time electricity. They then get the Feed In Tariff payment for themselves.
2) You purchase the panels yourself (two options here). i) You can then either opt to get free daytime (daylight) electricity and pay for non-daylight electric or 2) you can opt for a deemed rate which will pay you the FIT for 50% of the electricity you harvest.
The FIT's is pretty generous £0.43 for every kw you send to the grid and £0.03 for every kw you harvest (so you get £0.46 for every kw you send to the grid & £0.03 for every kw you use yourself).
The return is that good that companies will pay for the panels to be fitted on your house but reap the real rewards themselves (personally I would not go for the rent a roof option). Also if someone else owns the panels it could make if difficult for you to sell the property, if you own the panels the sales is straight forward and the purchaser would not have to sign any contract with the solar company. In my opinon if you intend staying where you are longterm and have the cash to buy the panels go for it. However, if you need to borrow the money this may negate any return you would get. Get as many quotes as you can I had a 4kw system and had quotes ranging from £12k - £30k. Also research the panels you will find that some are more efficient than others and merit the additional cost. This may help:
http://sroeco.com/sol...fficient-solar-panels