If you don't have a bike, or one suitable for commuting to work, it might be possible for you to get one through a Cycle to Work scheme run by your employer,and pay for this in instalments straight from your salary. Your employer has to be running a scheme before you can get your bike as the scheme can only run through what is known as a salary sacrifice, where you agree to temporarily reduce your wages to pay for the hire of goods - in this case a bike and equipment. The scheme is available to UK tax payers who pay PAYE, as the discount you benefit from is from Income Tax relief on the amount you borrow. You could save up to 40% of the amount you borrow through a scheme like this.

If you don't know whether your employer is already running a Cycle to Work scheme you could contact your HR, Payroll or Travel Plan team at your workplace to find out.   There are many schemes available. 

http://www.direct.gov.uk/en/TravelAndTransport/Cycling/DG_190101 has more information on how the schemes work.