My Ideal boiler ignites as soon as the hot water or central heating is put on but only stays alight for a few seconds and then goes off and a few seconds latter with water still running will ignite again and will keep on doing this,ignite...off...ignite....off ?

Simon Tyler, June 2011

Plate heat exchanger is most likely scaled up, replace it and fit a combimate as well

Boiler Bill, July 2011