Beware a scammer
I have halted the deal now, but if anyone else sees a similar transaction brewing, the general advice is to please be very, very cautious and only proceed if you are absolutely certain it's genuine.
I've had a similar experience when trying to sell wheels in the For Sale section. I was asking for £180 for the wheels but received a cheque for £1800 from a buyer claiming to be in France. The scammer asks you to pay the cheque in and arrange for collection with their shipping agent and to refund them the £1800 less shipping costs and the cost of the item for sale. The cheque is bogus but it would take 5 to 6 working days for your bank to get back to you by which time the scammer has collected the goods and you have refunded his "overpayment" from your own funds.
Fortrunately I was already aware of this type of scam so played along with it just to waste the scammers time and keep him away from other people.