Cheers Paul
Hmm, I had a problem couple of months ago, the temperature gauge was edging up from half to 3/4 if I drove over 65. and generally was higher than normal, 1. I changed coolant, and thermostat, (Still hot) 2. changed temperature sender and checked wire (still hot)
Then I looked at the back of radiator 50% of the fins where missing , rusting away.. funny looks OK from front, but when the radiator was removed the fins were falling off,
Solution , change the radiator , refill coolant , things are fine now, running at half on the gauge.
I would check several things before going on a long trip, I found this site, when I was checking my landy for my last 1000mile trip .
diff 6000mile service
Good luck
Craig