Fixed our Jazz permanently today - great result! Disconnected the battery, threw the keys over a nearby hedge and went out for a drive in the MG RV8 - even had to wind my own windows up and down and have an extra Weetabix to battle with the unpowered steering!
Seriously though, many thanks for the many useful replies regarding reducing sensitivity or switching off altogether - I had actually fallen asleep in the armchair whilst reading the manual, looking for solutions.
Ian