glow worm boiler stopped working - lights flashing indicate Thermistor faul?

thermistor lead plugs into pcb and runs up to the top right middle back and down.it is held in place by a length of wire to stop it being pulled out,remove wire and lift out thermistor(long copper tube in two pieces so it's easy to get out)I have a 60FF and have ordered a new thermistor £38 from local shop but I can see online £20 +vat.The leds on bolier indicate thermistor fault(left flashes slow and right led flashes fast)boiler will not fire up the fan comes on but no ignition.
As far as I know the thermistor measures the temp of the bolier so it knows when to switch off when water is hot enough,it it doesn't work the bolier cant light up as it would get too hot and fail,so the thermistor is a saftey device aswell.

Simon
March 2010

what model is it ?

barry
November 2007