Payment up front before doing anything for exterior door and frame fitting

Sound a bit strange. When you say he hasn't done anything, has he measured up and showed you different designs? Not all window places give you credit so I understand if he needs the money to buy the door. Why don't you tell him you can go to the suppliers and pay for the door? If not, post a job on here and get a great service :)

Bit suspect really, unless you're having a hugely expensive door and he wants it to pay for the door, but if so, go to the supplier and pay yourself either in person or on the phone or write a cheque for the supplier that he can use. If he wants the money for everything including labour, steer clear, there's no need to be paying up front for anything.

wouldn't touch him with a long pole only pay when your happy if he's a good chippy then this wont be a problem

Just pay for materials upfront maybe source the cost yourself so you have an idea on costing then you should be fine