We lost our apparently 'booked in' builder because he turned around at the last minute after several emails, in which he never mentioned he'd want a holding deposit; and despite not being able to start for 4.5 months.
We had a problem with this for two reasons; we'd never heard of this approach and it seemed a bit jammy, and we'd secured a loan for 4.5 months time not some now some later. When we said this, he offered our slot to someone else straight away and did not wish to negotiate further.
This guy's on the Federation of Master Builders website sure, but it seems to me that certain (South West London) builders think that they are in a class of their own and their wishes are more important than the clients'. Sorry I am a bit fuming as it's just happened; possibly we should have swallowed it gratefully and nabbed this guy cos he's 'that' amazingly good.