Good luck with this, Paul. It looks like a good 'un.

It doesn't seem unreasonable for folks to pay for tickets if they say they want them. Then, if they really can't make it closer to the time you haven't lost out financially. If, however, you manage to sell the unexpectedly spare capacity to any waiting list, you can refund the money*. That seems much more fair than reserving tickets on a no-risk-to-the-punter basis.

*And it doesn't seem unreasonable to subtract any expenses incurred, like bank/Paypal charges and/or postage.

Oh, and happy Christmas to you and and the happy KffCers!!!

--
Hamish