Out of interest did you try Budget in Bridge Street? The last couple of times I've had to buy an exhaust (not for the Mini) they were the cheapest by quite a bitHey
I replaced my back box in my o2 plate in May. I got it done at Mcconechys in Paisley for £154 including vat and fitting.Kwik fit wanted £199 I called Mini too and had a little chuckle at the price and so did the parts chap on the phone at douglas park and told me where they get their parts from Bosch and to call them.
hope this helps