I totally understand Ian and at four years pay back time it seems a bit of a no brainer.
5.5 pence per KWh is a disgrace there is no doubt about that so keeping all that lovely sunshine induced electricity for your self makes perfect sense.
Not to make you jealous but I got into the home solar panel deal about 12 years ago and will be getting 67 pence per kWh generated from April this year. The agreement runs for another 13 years.