20 tube panel. Wall mounted, below window, above flat roof.

[sws]

As I have a south facing rear wall on my house, I found I could install my panel right under the bedroom window angled at 36 degrees to horizontal. The airing cupboard with HW cylinder is directly to the right of the window giving me extremely short pipe runs (I only needed a total of 4 metres of 15mm) and therefore I have minimal heat losses.
Originally I had planned mounting the panel on the flat roof, but the buildings regs department went overboard on requirements should I want to attach the panel to the roof. So, instead I bolted a triangular welded box section mild steel frame (treated with Hammerite paint) to the wall to take the load and rested the lower corners of the panel on a couple of old pallet planks on the roof.  This system the buildings regs guys were happy with. The benefit of fitting it like this means it is very easy to access should I ever need to work on it. But the window cleaner whinged a bit!!

[sws]

I couldn't get all the pics on one posting so here is another

[bqjohn]

looks like it would be quite easy to add another 20 tubes if you needed it as well.