Baxi combi 105e occasional flame failure light?

Home someone can help with this - we have a baxi combi 105e boiler and over the last few months it has stopped working with a flashing light indicating a flame failure. Resetting it fixes the problem - CH/HW all working fine. Its happened a few times and a little more frequently over the last few days.

Any ideas? I've gone as far as taking the cover off and giving it a good clean but thats my limit with boilers :(