22mpg unless you drive like a granny. Tyres are £100+ a corner and you'll get through a front set every 20,000 miles or even sooner if you drive it hard, unless you have the wheels PROPERLY aligned and the camber correctly set (hardly anyone can do this, including main dealers).
You will enjoy endless, very expensive, repairs which you will have to do yourself or you will spend all of your disposable income on garage labour charges.
Your oil cooler will fail and/or your HBV which in turn will ruin your dis pack which cannot be reached by normal humans. (I know becaue I tried it today - and failed)
Your central locking motor will fail in your drivers door so you will have to open the back door first and reach round to open the drivers door (as long as your fingers aren't wet), your ignition barrel will stick so you can't turn the key start the car and your glove box handle will break.
Your scuttle drain will get blocked and flood the passenger footwell in the winter.
Your crank sensor will fail regularly which will cause the car to stop wherever it is, whenever it happens, which will be quite often.
Your alarm power sounder will set the alarm off every couple of hours at night until it spontaneously combusts and destroys the car. Unless you remove it as described in these pages.
Your headlamps will cloud over. Your brake pad wear sensors will break, while you are putting them on.
You won't be able to change the oil filter because the cap will seize on and not even your local garage will be able to get it off without a power saw.
You cannot change the spark plugs without taking half the engine to pieces.
The exhaust system costs £300+ and you can no longer get an original GM system that lasts a few years (I think I bought the last one). I think you nowhave to import one from Germany if you want a decent one.
Every part you need to buy will seem to cost twice as much as it does for other cars. Even with a Trade Club card.
Every fixing on the car is made of blancmange so when you want to undo it, the head melts. This is particularly true of the transmission plug and the oil drain plug. This largely irrelevant since nearly every fixing on the car is inaccesible anyway.
BUT, when they are working well they are an absolute joy to drive. I've had mine for nearly 7 years.