Many thanks to Matthew and Esther Phillips for their information sharing on the eco front. They have sent through a couple of links which are really useful:-
http://www.kyocerasolar.de/products/solar_faq.html which is an easy read FAQs on photo voltaics.
http://www.naturalinsulation.co.uk/cms_items/20060607164406.pdf which is the result of research paper about making buildings 'breathable' and why it's better all-round than the modern technique of trying to envelop buildings in impermeable barriers. This is especially important for old buildings with their stone walls without damp-proof courses. Like ours! Be warned this is not an easy read unless you are a boffin. Still not sure what meaning to take out of that one.
Thanks also to Mark & Lauren who added a comment to the previous post with a couple of useful links to pages of links. I will plough through them but I am impressed with this site purely for its numpty proof, plain speaking information.
Next steps for us is to work out what power we need to generate and how, then identify what implications that has for the roof design so that we don't end up having to alter the roof after we have built it. Just seems like everything needs to be considered in detail before you start anything. The biggest nightmare is establishing where to start as there seems to be so many variables.
Happy New Year to all!