I'd make a complaint to your Credit Card company, take a screen shot of the 'offer' still being on the site. This is bad news if people were tricked or misled.
Or call mecca direct and complain:-
Customers calling within the UK phone:
0800 0831550 - That's mecca's number
Monday - Saturday: 8am - 10pm
Sunday: 10am - 10pm
(All times are London local time)