2002 1.4 8v petrol intermittent starting problem

My wife has a 2002 1.4 8v Fabia which has had an intermittent starting problem for several months now and my garage has not been able to locate the problem. Here are the details:

It will start perfectly 90% of the time and once started and warmed up always runs perfectly. The other 10% of the time the engine will turn and either not fire at all, or eventually fire and sometimes start on 2 or 3 cylinders. If I can keep the revs up for a few minutes it will clear and then behave perfectly from then on. It seems to be limited to cold starts but does not seem to correlate to either wetter weather conditions or how long the car has been left unused. I can smell fuel so I dont think it is a fuel problem. I have replaced the coil pack with no change seen. Spark plugs are also new.

The garage have checked the fault codes and only misfires are recorded (not surprising) but no other clues are seen.

One other point to mention is that it does loose coolantbut neither the garage nor I can find out where it is going. I originally suspected head gasket (small amount of mayo under cap) but the garage has carried out all manner of checks and can find absolutely no evidence of this being the problem.

I would be really happy to hear of any suggections since it is beginning to drive the my half, and therefore me mad!

Thanks, Andy