Hesitant running at low revs

Hi

I've noticed the last couple of days that my vrs is not running as smoothly as its was.

Its a 2006 2.0 vrs.

I have only noticed it at low revs and in low gears.

I've not had this problem before, its got a full service history and is showing 80k and  still returns a good mpg.

Its normally running on shell v power but had a tank of Tesco momemtum the other week. Its had this and run with it ok before

There does not appear to be any other problems.

Has anyone got any ideas,

THanks