If you press the grey knob for lighting the pilot light,it should go in quite a bit when pressed. If not try turning it clockwise and anti-clock a couple of times then leave it for up to 3mins. In the 3mins the pilot unit should reset (with a click noise). Then try lighting again, if it still won't light it sounds like the pilot unit is faultly. Never changed one so I don't know whats involved (sorry). Hope this helps. John.
John martin
April 2008