>>>In the end I want a fun car with enough power to hold my own on the motorway and with a decent amount of kit.

The majority of cars that age and engine size will easily hold their own on the motorway, some might get to the required speed a second or two quicker. If you want fun, I guess you mean good to drive off the motorway on the twisty bits. Focus Zetec with the firmer suspension. If you want the kit then go for the Titanium which will still be a great drive. The Focus won't be as quick in a straight line as the bigger engines VW powered cars, it should be cheaper to tax and fuel though. I'd scrap the A3 idea and go for a Golf or Seat Leon or Skoda Octavia if you fancy a VAG engineered car and save a fair bit of cash even thought the Audi (and Golf) should hold their value a bit better. The extra miles on the Golf and A3 shouldn't concern you unless you only keep it a short time.

There are plenty of independents around able to service and repair those cars at reasonable rates.