why do you have to buy a decent bike!?
a cheap and cheerful will also do the job. I got an ol' Peugeot road bike for a bottle of whisky, and its doing me the world of good.
I took the drop bars off it, singlespeeded it, and use it for riding to work. Its a blast and keeps me fit at the same time!
also like the odd stint into the countryside for a couple of hours on it!