Basically the gearboxes are going left right and centre in MK3's. Both 197's and 200's. The most common reported issue crunch at high revs between 3rd and 4th.
That's exactly what happened to my 197. 4th gear synchro went. It wasn't even at high revs though, it just crunched in to gear every single time. Luckily mine was just inside it's warranty period. It hadn't even had a hard life like my previous Clios.
If anyone is buying a 197 Cup I'd steer clear of my old one (number plate ends SXY). One of the reasons I got shot was it was out of warranty and the gearbox was starting to feel a little on the ropey side again.
TBH, when they're cold the gearboxes really don't like doing anything!
I've not really worked out my MPG, but with my mixed driving commute (normal roads in to Birmingham, M6 home) the trip reckons between 28-30mpg normal boring driving. I used to see 32-34 in the 172/182/Trophy. However, the tank is a little bigger in the 197/200 and I seem to get an extra couple of days out of it, when it should probably only manage one more. I think the 172/182 was a little generous with it's readings to be honest. A full tank in the 200 gets me around 340 miles, with the light coming on soon after. They really hate stop start traffic though, I've never seen a fuel guage in a Clio drop so fast!