I can't comment on the Cupra, Clio or Civic as I've never owned them, they were just examples of fairly quick cars that are a massive step up from a Micra and will provide you with most of the things you want.
I can comment on the MR2 as I own an 1997 Revision 4. As far as I know rust isn't an issue on these unless you get a paint chip that goes through to the metal and don't treat it. This is a problem with all cars though.
The MR2 handles brilliantly, it's pretty quick, it sounds great, it's cheap to run (35mpg average etc), it looks brilliant (I'm obviously biased), it's very well made and reliable with no major issues to talk about, it's lost about all it will ever do in depreciation.
I don't think you are being too picky at all. Afterall you have 8 grand and that could buy you a car that wont need many repairs and will be in tip top condition. What I'm trying to do is challenge why you think that you need to spend that much to achieve what you actually want from a car.
It's as simple as Depreciation vs Repairs. The fact that you currently own a Micra and that's what you're used to, you aren't reliant on the car and you've never actually bought a car and sold one and therefore haven't experienced depreciation, this means that in my opinion spending 8K now is unnecessary and risking the odd repair is worth it over having a lot of guaranteed depreciation.