The problem with M&S's pre-booking service is that, while you can view online, you still have to take the form into a store!
The best way to get a definitive answer to your question would be to contact M&S direct:
http://www2.marksandspencer.com/help/contact/contact.asp ?q=sto
Anyway, what's all this about pre-ordering? It's much more fun if you leave it to the last minute!! (I once started my Christmas shopping at 3.20p.m. on Christmas Eve - and that included cards that were destined for Australia!).
Chris