Maybe just get slick tyres? (i.e. the smooth ones)
If you've currently got 'grippy' mtb tyres you'll feel a world of difference.
Not as good as a road bike of course, but better on the wallet!
Yeh that's true, if I get injured and have to cycle more I will definitely get some! I had them on the old bike but they got wrecked when I got knocked off.