No one gets anything for nothing, do not be taken in by this obvious set of repeat scammers. Send the paperwork back to them (without your name and address) in the resealed envelope provided. Mark envelope “Cheque inside” (or similar wording). DO NOT PAY POSTAGE on your letter.
I would suggest paying a visit to the shysters next time you pass through Ross on Wye but we only have a post box address and GBH for such people is illegal !