I can get it to light but as soon as I release the button it goes off again, am i missing something?

Eleanor, September 2008

If the flame wont stay lit after holding the pilot valve open for 15-20 seconds then it is 99% due to a failure of the thermocouple.
You don't say which boiler you have got but most plumbers outlets sell universal fitting thermocouples but check before you buy. Cost should be less than £15.

Cledlyn, September 2008