Multispace 1.8 petrol strange idling problem

[GSLondon]

Hi all

Sorry for asking so much and contributing so little!  My Berlingo has developed an odd thing over the past day or so. Basically the idle speed is going up to about 1,400 rpm when in neutral, having just stopped, or is slow to go back down its normal 1,000 rpm idle speed.  Probably not explaining it too well - apologies - but I suppose it's like a sticky accelerator cable, except I'm not sure that it is.  Any ideas?

Many thanks