not quite right

our new (56) fabia doesn't feel right. in 4 months, it has registered a misfire on number 2 cylinder 3 times.Despite being back to the dealer and having the AA (skoda assist)replace a coil it still isn't running right. Basically, when running on a cold engine it is nice and smoot but as soon as it reaches running temperature it appears to miss between gear changes at low speed. At motorway speeds and above 1500 revs its OK.It has just had a full diagnostic that showed no faults but it's not much fun to drive round town or in traffic. this is the first skoda we have had so we don't really know what it should drive like. Does anyone out there have any ideas???

isaao