Car jerking at low throttle

So IACV all checked, throttle butterfly all seems OK, however with the engine warm if I take my foot off the accelerator at low speed the car jerks really violently until I press the accelerator again. I assume this is a mixture issue, but not sure how to sort it? Ironically the orange warning light isn't coming on.

If your foot is off the throttle the revs should drop smoothly.
How smoothly does the gas peddle move?

The pedal appears to move freely and smoothly - I only get the jerking at low speeds, no problem when I take my foot off the throttle at higher speeds ( over around 40mph)

I think you might need to see if there are any fault codes logged in the engine ECU.

You either need access to a T4 or Pscan. I gave up guessing on these cars (or any car) a long time ago (pre OBD and ECUs, it was a lot easier in many ways).

Pscan will give you access to a raft of info including fault codes and live data. I would not like to guess what is the cause. I would look at the vacuum and stepper readings for starters via Pscan.

I'll have to see if there is anyone near who would be willing to plug in and read my codes for a few beers or other suitable fee 😀

Best move. As these cars get older, components wear out and in my view, the cars become a lot more expensive to fault find and repair. Without something like PScan, it can become very expensive and frustrating. Buying an MGF for say £1000 is just the beginning and the cost curve will quickly climb without diagnostic software.

The car appears to be behaving itself again, no more "kangaroo petrol " symptoms so I wonder if it was some dodgy fuel ( I've done about 350 miles in the last three days so filled up twice with E10). I'll still try and get access to someone who can read the ECU codes and settings as I not convinced there isn't an errant sensor in the fuel train.