I don't know if I can describe this very well, but here goes...

While warming up, the engine repeatedly revs every second or so briefly. When warm (if it had a choke I would describe this as when the choke comes off) it sounds fine.

Driving ok, but if I take my foot off the gas it seems initially to slow very quicky, as though there is nothing happening in the cylinders. Then the engine cuts in, then out, in, out repeadtedly. So it's sort of a jerky motion. But only when moving, when stopped the idle speed seems fine.

Anyone had anything similar to this? I did have a problem with the engine cutting out completely a few months ago, but I got a new speed sensor and this solved it. Don't know if this is relevant.

i think you are describing over-run... ie... driiving along at speed then taking foot off accelerator.... have you had the throttle body off at all? or disconnected the battery?

sounds like the adaption values for the throttle body need resetting

yes was about to say the same. disconnect the battery for an hour then reconnect and switch ign on (dont start it) leave for 10 mins to allow it to reset the throttle body and it may be better.. also worth cleaning it inside while the batt is disconnected (the throttle body not the car that is)

Ok will give this a go. Thank you!