Potterton Boiler Fires Up When No Demand?

Hi all.

I wonder if anyone can help with this.

I have a Potterton Suprema 60 boiler which seems to fire up even when there is no demand for heating or hot water. My gas bills seem to be higher then they should be given the amount it's used and I think its because of this.

I know some boilers have a 'warm start' type feature to keep heated water more readily available but I don't think this boiler has this (Can't see it in the manual)

Any thoughts on what could be the reason would be appreciated.

Thanks.