Well, er, not knowing what you have and don't have already...

Buy the three-season boxset of Black Books. Don't even question it. Buy it. This is comedic genius at its absolute finest.

Or, if you've already got it (no other excuse is acceptable :p) buy Flight of the Conchords s 1, or definitely first two seasons of IT Crowd, or any/all season of Boosh, or maybe the Boosh Live DVD?

Yes. Hopefully this may point you in some sort of direction.