Are you sure the Tme clock and Cylinder Stat is calling for heat, if fitted is the Motorised Valve opening?
if so is there 230vac at the L/N terminal at the boiler, and at the Gas Valve Solenoid?
its just a matter of illimination
www.gassaferegister.co.uk will assist you to find a Service Engineer in your Area
www.elanar.co.uk, May 2009