Duncan, not sure if its all still an issue but I worked until recently as an estimator for a construction company and may be able to help. I am only along the road aways at Leatherhead and have done the domestic installer course so have a good understanding of electrics and pricing, I am not touting for doing electrical work as I am not qualified but I do know some electricians and other contractors who may be able to help. If your interested please PM me and I will try and help.