So you'll be doing roughly 20k a year (give or take a bit)
It not worth considering a diesel? If it were me I might consider a rs megane (dci) 175, fabia vrs, or even an octavia vrs (diesel versions available)
My dad's soaked up LOTS of miles in recent years in Saab diesels. Still gets high mpg(~55) out of a very high milage 95 diesel, so you could easily look at the likes of a 93
There's plenty of great motorway cruiser cars around if that's what you're after (Audi, Saab, BMW, Volvo, merc etc...)
If you were after something flashy and your budget would stretch my folks have a tt convertible with a diesel engine that's immense, so something like that would give you style too. Then again, there's lots of convertibles around that can give you a half decent mpg