okay, update.
The admissions tutor replied saying that all letters (for Magdalen college) had been sent out by 19th December, but my letter had bounced because they had typed the wrong address into their database.
Apparently the first line of my address was too long for their system -.-
anyway they offered to fax the decision letter over (because they apparently are not allowed to notify students of decisions by email) so I'm presently waiting for their fax
(hope this helps the rest of you in some way)