Iv found about 200 watts does the job for fridge and TV, with a good reserve in the batts. Good batteries are important and I'm a fan of gel and agm, however don't buy cheap ones.
There is a picture on my profile showing two 12V 60W panels (120W total) mounted on my clansmans back rail. As you can see they are quite big, so that is an element to consider. On a typical sunny day (not overly hot) I can get 7-8amps. Remember in DC, P(W) = I(amps) * V(volts) , so 120W/12 =10amp rating, but that's a rating in best conditions. Also the Chinese make some really good/cheap regulators that have lcd displays that tell you production stats, batt volts etc. I will try and find out what model I have.
I have not used the whitworth panels, I personally would buy panels from a solar shop or ebay, known brands.
My answer didn't really cover your question, but just my thoughts out loud.
I haven't done it yet, but I'm thinking of mounting the reg in a tupperware box to waterproof it. The ones with the rubber seal and clips. As I doubt these things are very rust proof.
