What pearls of wisdom can you offer me?

[Nimble2014]

I have planning permission to build an extension to our house. Building regs are about to be filed. I've got the names of a few recommended builders. And now I'm frozen with indecision.
How can I ensure builders quotes are comparable?
Do I need a quantities survey? If I do, does that mean I have to decide on all finishes and fittings before I get the survey?
I have ideas above my wallet - do I ask quotes for everything I want doing and then cut back/out items to meet my budget?
Any and all advice would be most welcome.

Bump?

Do you have an architect? We had an extension to our house, and the architect dealt with planning/building regs etc. They also arranged all surveys etc.

I don't think you need a quantity survey, afaik that's mainly for commercial building work. But someone else might come along with more knowledge than me.

Yes ask builders for an itemised quote covering everything you want, then you can cut back according to budget. Don't worry about finishes/fittings in that quote though, they'll just quote for fitting whatever you choose.

I don't have an architect- I didn't really believe we'd get planning permission so asked for a draftsman to do the drawings, because he was very cheap. Now that I'm looking at putting my money into the project I'm starting to think I made a mistake. How detailed do I have to be when I ask for a quote - ie do I need to specify brands etc?

And thank you for your reply

In an ideal world you need a schedule of works. This breaks down the job into individual components, which your various builders can tender against, so you can compare their quotes directly. We're doing a big project so did get a QS to draw up the SoW based on the architect's drawings. I suppose it might be possible to draw one up yourself if the job is relatively small/straightforward? The advantage of having a QS is that they will put a cost against each item so you can see if you are in the right ballpark budget wise (but of course they cost money!).

Ok - a schedule of works sounds like a step in the right direction. It is quite a complicated job, and because I'm an absolute beginner I think it would give me more confidence in the tendering process. I have had friends getting quotes for works that vary so wildly you're left wondering what they will end up with. I really want to get the planning right so that we don't go making expensive mistakes.