I'll try to describe this as best possible ;

Car has been running great.....until today

Pulling away from rest,fine until I tried to accelerate in 2nd gear.Felt rough until I change to 3rd.If I tried to accelerate hard in 2nd,it was terrible.Tried again on a quiet stretch of road and the emissions indicator flashed on/off (disappeared again).(this indicates an emission problem that could destroy the cat - according to the manual)

Car has covered 47K miles.Runs fine apart from this flatspot issue and also when approaching a junction and depressing the clutch,the revs drop really low then recover to 900(ish) rpm.Flat spot is noticeable in 3rd but much worse in 2nd.Fuel is from Tesco and is around 1/4 tank left. NO warning indicators while driving,all fluid levels correct.

Dirty petrol or something worse ???