Well today was I-day: installation day. A few people have asked me to update them with my experiences so here we go.
4 friendly men from our supplier came over and worked solidly (fuelled by 2 cups of tea and some cake each) for 6 hours. They discussed with me in detail how I would like the work doing and where things should go. They also discovered that my earth wire needed updating and did it without fuss and without charge (and will send over certification etc.). Obviously we are paying thousands of pounds to their company but it was a nice gesture I thought.
The work is less obtrusive than I expected it to be. There is a new box on the side of our house:, a wire going into the loft to an inverter obviously the panels themselves on the roof.
We can also see it is working as the meter has stopped going round (if it was an old fashioned one it would actually go backwards! I had a look about half an hour ago and we've already generated 1.7 KWH in a couple of hours. Obviously it's a sunny day so that helps, but the payback period starts now!