I have just bought a new bike for almost the same reason. I have a knee problem and have to ride uphill to work.My new bike is a Raleigh Pioneer. Cost about �220 which includes �50 worth of accessories but is well worth it. I bought a second hand one previously. That was a Raleigh Pioneer Classic. 5 years old but almost new. Ive had it serviced and oiled etc, costing me �25 but doesnt seem to have enough gears on for me. Im selling it for �50. I live in East Yorkshire if its of any use to you.