Well I took a look but the promised rain came on almost immediately so
I've called it off for the day. I think I found the throttle
potentiometer - a shiny round metal component on the pedal axis.
Problem now is going to be actually getting to it without taking the
drivers seat out. Its tucked up tight into the corner of the drivers
footwell behind various obstructions. There isn't any obvious signs of
dampness or corrosion from what very restricted view I did have so I
might have a search round for a local small firm diagnosis service
since the agency were talking £80 plus VAT. At that price I could
justify a connection lead and some software if its anything like
reasonably priced.