Hi again,
Have found a mobility product online- a kneewalker, looks a little like a child's 4 wheeled scooter, has an elevated platform along which you rest the lower leg and handles for steering. There is a video clip of it in use on the site.
I don't know how I will get on with it but as weekly rental is very reasonable am willing to give it a go.
Will let you know.
Many thanks for your advice and prompt replies.
Regards
Jane