Acceptance of quote is it legally binding?

Only if both parties have signed the contract. By law the builder has to give u a 14 days cooling off period thanks. Michael Reid

Yes it is for the work on the Quote. They can be ajustment to the quote if un for seen areas for example. digging foundations into clay and the building control states we need to dig another 50cm that my cost more in skips and labour. If this si the case it should be writen on the quote.

No, a contract is though.

No

Depends if youve signed contract .