does it take to change a light bulb?

no...now really..

how many cats in a classic uk turbo exhaust system?

I thought just the downpipe and center, but a mate of mine is also saying that the uppipe also has one?

 

Assuming all classics are the same, which I believe is the case, then you are right and your mate is wrong. The first Cat is in the DP just after the turbo and the second is in the centre section about midway between front and rear wheels.
Kevin

 

Hmm ok cool thanks