My Chaffoteaux Britony 100se combi fails to ignite in CH mode, it works fine in HW mode!?!

When I select CH mode the 30, 40, 50, 60, 70 & 80 neons light up in sequence and then go out and nothing happens, no light stays lit to point me in the direction of the fault!?!

Replaced PCB and still the same problem!?!

Help

Mr Tilley, November 2011