Please note that if you add a small electric motor to your bike and use that as a help getting up hills, you can bike mostly anywhere, flat or not.
Some problems with this: Electric bikes are expensive (like £2000 vs £200). UK Government regulations make the status of electric bikes dubious, particularly the more powerful ones needed to ride up hills. If no one else can afford to cycle or is allowed to cycle, this prevents a mass of cyclists which would make the road a bit safer.
I'd really love for there to be both government will and a solution to the price problem here.
http://www.atob.org.uk/electric-bikes/electric-bike-legislat...
http://www.bikeradar.com/gear/article/electric-bikes-and-the...
(Edit, better link)