Builder recommendation

[springmachine]

Can anyone recommend a builder suitable for a small single story extension project in South West Hertfordshire?

It's just an 8m2 simple box with no need for knocking walls or structural steels and have had quotes coming in at over £20k so far not including internal flooring, decoration or external finish.

Guessing the job isn't of interest to these builders as I had expected around £1500-£2k max per m2 fully finished