In message , .
writes

Another factor would be the difference in value of my house before
and after extension compared to the cost.

I think in general a good extension adds more value than it costs ,
but I know that isn't always the case.

here's a gift to you and the other diy'ers who ought to know better.

A gift ?

pretentious **** - it costs £100



get a copy of UK building costs blackbook from Franklin + Andrews
http://www.franklinandrews.com/publications/hutchins/ it's not THE bible
but it's what quite a few tradespeople use to generate /estimates/ from.

estimates, mind. not quotes, but it will give you your ball park figure
from which to gauge your opponents. it will also help you to think
clearly about exactly what you want by way of building works.

hth



--
geoff