Practicing vs Practising

[faustus]

For some reason I've always been convinced that practice works like advice - I advise you, but I give you advice. You go to football practice - but you are practising football. (Are you or have you ever been a practising accountant or a practicing accountant? May be you'll get better. I'd write with an s. You'll be in a practice.)

The phrase in question is "practicing media theory" in the sense of undertaking, using a particular theory - but it just tastes wrong to me. (It's complicating by the need for it to have a second sense of the theory of how to do practice.)


Any thoughts?

Edit: This would be UK usage, in case there's a difference. Google gives Practising over Practicing by only few thousand.