Unless I'm mistaken, the Pro-drive exhaust is only back boxes, isn't it? That would only make maybe 2-3bhp over standard. My system was stainless steel straight through from the cat-back, so that's quite a difference. Go with a Vortex as well and you're looking at a better improvement.
It's a light (relatively) car, so small-medium improvements are noticeable. The other big advantage was that the throttle response improved quite a lot once the Vortex was installed. This means the revs climb quicker, and that means you can roar up to the redline more easily which I found satisfying regardless of power gains.
Re MPG, with all the mods on board, my average climbed from 21 to about 24.5, for London suburb driving, which is a nice step in the right right direction. After mods I occassionally got 30mpg on the motorway, but due to generally spirited driving (i.e. wherever the traffic was light) my motorway trips usually came out at 27mpg. Not that bad really.
Thing is, it's either a case of do the mods or go for a 1750. I don't think there were any 1750 Ss, and a 1750 would never sound as good as a 2.2 anyway. A fully modded 2.2 makes a great sound that puts a smile on your face, and has a wide range (revs up to 7200 revs). A 1750 would be faster (if also modded)., but there's no point revving it past about 4500-5000.
Finally, my remap was done before my final exhaust (Vortex) and induction (K&N) changes. I suspect the car would have got a few more bhp if it had been mapped a second time. This is because Im pretty sure it was running too lean at high revs once the Vortex was on. The car was drawing more air at the front and revving more freely; really I should have had the fuelling increased by getting it remapped again but I never got round to it.
Brat Pack no.8