I own a Fabia 1.2 comfort hatch.

Recently the emissions warning light ( orange engine icon ) has come on.

I took the car to my main Skoda dealer and they did a full diagnostics check. This check revealed NO problems and the light was reset.

One day later, the light has come in again, can anyone offer any advice please?

It could come on for one of many reasons, it should have had some fault codes stored which will be the starting point for any diagnosis.

Has the car been running OK? down on power misfiring, has the temperature gauge been working correctly - not dropping to 0 and moving back up?

Car is running OK, no misfires or temperature gauge faults. Dealers diagnostic checks indicated no problems