I looked through the tech archive and found the article about the icv - it seemed to be for the older engine (my oil filter housing is plastic, the one in the article is metal) I couldn't find the icv valve, so I took off the air intake pipe at the throttle body and sprayed a load of carb cleaner in - the workshop was full of smoke, but I didn't notice with my head under the bonnet! It made a slight difference - but still feels lumpy. Got back and discovered this - United Bimmer - BMW Enthusiast Community and Forums : Bimmer Technical Help
- more indept and I think I know where to start looking now!
Checked my tyre pressures while I was at it, down an awful lot - so pumped them to correct pressure; now I can hear a knocking from the right hand front wheel when I'm turning at low speed or braking. (checked this out - inner tie rod, wasn't that noticeable with lower pressure in the tyres)