Calculating ideal azimuth for solar panels

I am thinking of adding a combined sunshade/solar array to the WSW side of my house. Normally the ideal azimuth is due true south (not due magnetic south) however due to severe shading this wall receives no direct sunlight until noon (13:00 in summer).

So, how do I calculate the ideal azimuth under these conditions? I’m assuming seasonal variation, in which case I prefer to optimise for winter.

I am planning a frame with front and back rails parallel to the house wall with panels mounted at an angle on it.

Probably not much help directly, but if you can implement something yourself or wait for someone else to, Google has released a new APIs which cover the UK and can do a lot of these sort of optimisations.

Thanks, I’m sure the links would help some people but I’m afraid I wouldn’t know what to do with an API, even if I recognised one.