Well got my sat nav home and couldn't get it off demo mode, rang Halfords who talked me through it but it still would not come off demo mode. Then rang Garmin Tech support gave them the serial number and then found out why it would not come off demo mode. It was a demo only unit had no internals or GPS chip set so obviously would not operate as a navigation device.
Took it back and the best offer was a refund
Apparently it's only the Garmin ones that are demo units the rest are really ex display functioning units.
Lesson learned and I should have stuck by the old adage if it is looks too good to be true it generally is.
SWMBO not happy and going to press Halfords further whilst I'm away
So well and truly peed off