In my area, Christmas cards and seasonal Wrapping Paper are Not to be put in with other papers for recycling because there is so much glitter on a lot of them which messes-up the recycling process.
I understand that all through January Marks & Spencer will have collection points within their stores. Also a number of Supermarkets (such as Sainsbury) in certain areas will accept Chrismas cards.
All the supermarkets round here have recycling boxes, but are you thinking of a charity which makes them into tags, etc? Perhaps your local Age Concern shop make take them for something like that - or your local primary school?