Bongo Fury

My air con makes the engine sound like it is trying to tow the QE2

I know the older air cons seem to run the compressor direct from a belt, but it does seem to make a big difference to the engine revs. My modern Leon MkII sounds no different with a/c on or off... presumably because it is a modern electronic system.

Could I just have a stiff bearing or is this just normal?

The engine revs should increase slightly via the cold start vacuum solenoids when the ac loads up, a lot of peeps don't though (maybe broken solenoids/vac pipes), even so the revs should only drop slightly. Is this only noticable on tick over, or when you're driving? could be the extra noise is in fact a screwed bearing or pulley on the ac compressor, difficult to say without knowing/hearing what exactly is happening.

Also check the tension of the belt. If it's too loose it will make a screeching noise when the compressor is engaged.