/I assume they only started to flash when in the switched off state!
If so this is a classic example of inductance from the other lighting cable causing the flashing. Putting one of the halogen GU10s back in to see if that stops the flashing is the simple test before fitting the suggested item.
Cheers /Q
Aha! Yes when the led equipped fittings are off, operating the kitchen lights (all traditional bulbs) makes the leds flash once.
Tried a halogen gu10 in each light fitting (each has 4 x gu10s), to my surprise they all still flashed when other switches operated, including the halogen gu10 (more of a glow than a flash but definitely visible)...
So seems my initial thought for a solution won't work?
What next please? Cheers
Jim K