David, I think you are being unnecessarily pessimistic. We have got planning permission and in the process of sorting building regulations for our extension - and we had the additional problem of having to get Listed Building Consent as well. It has been slow, but we have got there
Of course builders do not like to give sure quotes for a building project, all kinds of problems can arise that cannot be foreseen. Builders found a completely redundant and unused drainage system under the ground DD's extension was built on. This had to be investigated, removed and filled in, which inevitably meant extra cost - and then there will be all the changes that may be made during the project, usually because the house owner keeps changing their mind - have you ever watched Grand Designs?
We have contacted several builders for estimates, and two are coming round next week to discuss the project. We may have to wait six months or a year for the work to be done, but I have more confidence in a company with a long order book,which suggests that they are sought after rather than one that can start tomorrow.