Thats a good question. I think its probably because I am being a bit of a snob to older cars, and generally want something with 50k on the clock which is relatively fresh inside and not looking a bit old and tatty.
Apart from a z4 that would then start to fall into the range, what else is there?
It depends what you're after from a car really...
You've made reference to low mileage and newer cars, do you really want that, or are these just qualities that you associate with a car that's in good nick, and that is what you're really after?
With respect, that is not going to be a difficult objective to achieve when coming from an old Corsa, and you certainly don't need to spend £10k to get there.
When figures like £10k are mentioned on a car enthusiast sub-forum, you'll get suggestions like an S2000, TT V6, Z4 3.0, 330Ci, ST3, etc, and they're spot on reccommendations for a car enthusiast with ~£10k to spend. You don't sound like a car enthusiast, you sound like someone that's sick of a old Corsa. Therefore, why spend £10k?
£6-£8k will get you a nice recent Focus/Golf/A3 if the age/mileage/latest shape is important to you, but you'll find that you usually need to borrow £5k or more to get the lower interest rates.
I'm far from being against buying cars with a sensible loan, so long as you're never in negative equity, ie you could sell it tomorrow for the amount you owe on it. If you're a car enthusiast, want something special and can afford to service the loan, then test the likes of the cars mentioned, buy your favourite and enjoy it as being considerably more special than a Focus/Golf/A3 etc.
People generally contribute to spec me threads with what
they would buy for the money, rather than considering what the OP's requirements are. Obviously I don't know you, but reading between the lines, and noting your preference for keeping out of debt, I wonder whether you really need a loan at all? You mentioned getting rid of a 2001 Corsa, and taking £2-3k out of savings, which would give you a budget of £3-4k.
I think that for you, relaxing the age criteria to up to 7 years and spending £3-4k on a 1.8/2.0 top of the range Focus/Golf/Leon/Civic (Maybe even a ST170/VRS/Cupra/GTI/CTR if you do fancy something sporty) as a cash buy makes a compelling case.
Don't be afraid to stray over 60k mileage either, at best you'll find yourself paying more money, and you might even find that an 80k car has had discs/pads/cambelt/etc changed where as you might have to foot the bill for that on a lower mileage example...
You say you're being snobby about age and mileage, but you may well find that the problems you're facing have more to do with driving a Corsa, than driving a car registered in 2001 that's covered a lot of miles...
You will find dogs at all ages/mileages, but as long as you buy on condition and spec rather than age and mileage, I'm not sure what a £10k Golf will get you, that a £4k one won't?