I've emailed them politely thanking them for advising me in good time but saying that I do not recall such a warning when I made the transaction and requesting a refund. No point getting irate about it just yet!
Just received this from Seatwave:
"We are unable to provide you tickets for this game as we are not
allowing sales to anyone who has not purchased tickets with Aston
Villa previously."
Also looks like they will not refund the money they have already taken!
Did anyone else do this?