Well i have a 95% success story to report from setting the TPS hysteresis to 0.05V - it stopped almost all of the hunting on the Rover.
The only bit it didn't stop was downhill on a (now) warm engine at 30mph on a trailing throttle. I doubt this can be tuned out due to the characteristics of the autobox - on a trailing throttle, it cycles the torque converter lock-up, the brake bands etc to increase engine braking.
In doing this it first brings one brake band in, then a second, the T/C lock-up all of which bring the revs up in stages then drop them again. This confuses the Leo slightly - the revs are up, the throttle is closed so fuel cut-off happens. Then the box lets go of the brake bands and T/C so the revs drop again.
All of this causes a bit of hunting which i doubt can be tuned out without losing engine braking which would force the box to try and brake harder which would no doubt exacerbate the hunting!
In fairness, this is much less obvious than the cold hunting so can be lived with and the 30mph hunting is now gone. The TPS hysteresis was set at something like 0.38V before - it was previously used on a V8 Range Rover (hot wire) apparently.
If this has almost entirely eliminated it on the Rover, it should completely cure it on the Jeep as not only is the Jeep much lower revving (about the same as a Range Rover V8 - 30mph/1000rpm in top, obviously due to T/C slip at 30mph it needs 12-1500rpm to attain 30mph though as lock-up doesn't happen until about 45-50mph) but the fast idle is also lower.
As an aside, i also increased the changeover delay to 0.7s from 0.4s to improve the cold change to gas on the Rover which worked wonders too.
Thanks for your help again Richard - very much appreciated!
Somewhere in Suffolk with a Jeep, 2 Rovers and a V6 Volvo