Thank you for replying so quickly.
Yes the fan behind the rear cover is working.
If I push the trip switch up into position it trips straight away. I have to unplug it and leave it a bit and then retry.
I works for maybe over 6 hours, with the inner fan going off and on over this period, but the radiator never freezes much just the first two rear upper bars. So it would only be a quarter of the radiator if that.
Thank you for all your help