Hi Linda,
You might have found someone already, but in case you are still looking we used
http://www.nickaustondesign.co.uk . They were very pleasant to work with and no headaches for us, as we let them design and project manage everything. We did pay the builders separately,but we used the ones they recommended and pretty much let Nick Auston deal with everything.
I can only recommend them.
Good luck
Fran