Your rams are the hardest thing but if someone could pass them on that would be good for you.
Its unusual that you would be asked to price the brick cleaning direct for the builder the cleaning down is usually always part of the brickwork package on new work refurb its a little different
And generally the bricklayer subs this element of work out
Your works ie the cleaning down should be covered in his rams
Never the less check access ie tower cherry picker etc etc who supplies as access is often impared due to landscaping being complete also think about protection to windows railings balconies etc
Builders wont hesitate to bang you for a few quid if they see evidence of any damage after the pressure washing
Get your quote right
Site visit is a necessity