hot or not?

Sounds like blocked rad to me.

Have had all the same issues as you. Is your sender matched with your gauge. If a 200tdi from disco, then change it for defender one, checking thread first. Ive done a lot of towing lately and needle went to max. Changed belts and all is well. seemed waterpump belt may have been slipping.

it was a blocked rad, new one fitted as it had had it, everything was fine until i switched the lights on and the gauge went back into the red, turns out the earth from chassis to engine and corroded itself off at the engine side, new earth strap fitted and everything is sorted cheers for everyones help!!