On 03/10/2013 10:22, tony sayer wrote:

Despite the ones across the way in the shade of the trees, are bolted
right down to the roof ..


That's probably a bad move unless they are the rarer tile type PV panels
that actually are the roof.

You want the air at the rear to help cool the panel as they work better
when cool.

There are a lot of cowboys out there installing PV in unsuitable places.