I'm not ignoring you, I've only just the notification of your original reply in my spam folder. That's now corrected so stuff should end up where I want it.

I think I'm probably suffering two problems in parallel. I had simply assumed the FPR was causing the poor fuel consumption as well. I can temporarily stop the stuttering (that usually kicks in about 3 to 4 miles into a journey) and dreadful idling by releasing the pressure from the fuel system by undoing the fuel cap, but the consumption I clearly need to investigate separately. Thanks for the info.

Nic