As already mentioned insurance for a brand new driver on anything fairly decent (as many car allowances demand), could easily be a couple of grand, in which case a car allowance doesn’t look so good.
A modern VAG* or BMW diesel with a modest output (318d Touring, 116d, the VWs you described, etc), will cost you buttons in tax and personal mileage fuel. I know you’re not a car nut, but one thing to bear in mind is the new 3 Series Touring to match the saloon just out is a year away still.
Hora – I know you’re the fountain of knowledge on all things motoring, but have you ever driven a modern (last couple of years) BMW?
Edit: * VAG = VW AG – VW/Audi/Seat/Skoda (and Lamborghini/Porche/Bentley of course, but maybe not relevant here :D )