I had an interesting chat with the Adrian Flux folks at Stoneliegh.
Given the perameters of my earlier post, they quoted £130 (I think, it's a bit hazy now).
However, as I had time to kill and face to face chat, I thought I'd get a bit adventurous/silly.
I asked for a quote on the same car but with a supercharger fitted (I had a small rotrex in mind). The answer was no difference!
Ok, lets get a bit sillier, how about nitrous oxide injection? Once they established the insurers and police would be happy, the answer was a 20% loading - £26!
So for £156/annum you could have a supercharged, nitrous injected Midas!
The nitrous would have to be kept to 1 or 2 x 25hp, smartly controlled so the gearbox stayed in one piece, but it would make an interesting drive....