When you turn up on Thursday, tell them that you have a number of customers who wish to move house and that for an upfront fee of £1,000, you will recommend their services to your customers. When they raise their eyebrows, inform them that you could do it for £800 as the £200 they want from you may be deducted from the £1,000 they pay you.
Hopefully the person you meet has a sense of humour.