The best thing you can do, knowing how little you do know right now, is find a shop and let them help you choose the right size frame, fit you to it, and then advise you on the gearing you'll need. Because Worcester = hills.
It won't help if you buy the wrong bike blind, off CL or another used bike site, and wind up hating to ride it. You don't have to spend really big bucks on a used bike, and some shops carry used bikes, too.
I would probably steer you to a triple crankset (three chain rings on the front) or a compact double with a wide range cassette.
Last edited by mprelaw; 07-16-14 at 11:39 AM.