I looked in to this a while back, wasn't worth my while and to get the best out of any system would be best installed on a south facing roof
npower install Schueco polycrystalline 170Wp panels and can install a system of any size or shape to meet your requirements. The smallest system that we install costs from £7,518 Including VAT and installation; this requires approximately 10sqm of roof space and will generate approximately 20% of an average households annual electricity demands. The average size of system that we install is 2kWp and costs from £11,848 including VAT and installation. A 2kWp installation will require approximately 20sqm of unobstructed roof space and will generate approximately 40% of an average household's electricity requirements. By installing a 2kWp system, joining the microgeneration scheme and selling the excess electricity that you generate as well as any Renewable Obligation Certificates (ROCs) that you accrue, you could save up to £280 a year off your electricity bill. In addition to the buy-back scheme, it is also worth noting that the government also runs a capital grants programme
These people will point you in the right direction
[email protected]
http://www.ecofirst.net
on another note, how are you going about building your own home, are you using someone like buildstore?