Sorry, coming to this a bit late
We enquired about getting some panels (we have a HUGE south facing roof) we ended up not going for them as it happens, but if you want a bigger set up look to the commercial installations.
I think the one we were quoted for was 4 times the size of a standard (is it 4Kw system normally?) for around £28K, but as we don't have the money sitting aside and would have had to take finance on it, it just worked out too expensive for us (what with having to still pay for electric when it's dark and having no way to 'store' extra power generated for later use)
I think it's a great thing to be able to 'grow your own' power, but unless you have the spare cash or a huge desire to be self sufficient, it doesn't give you the level of savings or income that it's portrayed to (by the
salesman who comes to tell you all about it - don't ask anything technical about it

) especially since they reduced all the FIT's etc.
I'm looking more to the small wind turbines myself now

Got plenty of that here
Good luck though and keep us posted with what you do BB
Karen