Had a problem yesterday with overheating I think? Engine started to lose power and then cutout after about half an hour. It's a continental with 100e engine, we were loaded up with 4 of us. I let it cool down a bit then started it and headed back slowly, water hoses into exchangers then seemed to cool down so water pump must be working. Any ideas?

Ok some questions, what was the temperature gauge showing?
Four up on a hot day..... flat out...?
If the temp was normal then as it was a very hot day I’d suspect either a fuel/vapour lock, ie the carb was too hot and or a lock in the fuel hose.
Alternatively ignition, could be the coil overheating and/or an electronic ignition module if you have one fitted.

If the temp was high then water flow round the heat exchangers, again an air lock in the rear cross tube is possible...

Intermittent issues like this can be a beggar to find.

Coil breaking down when hot? Simple to switch to rule it out.

There is no temp gauge but it was hot, the header tank was too hot to touch and releasing a bit of steam. The hoses were all very hot. I took her out again on Monday stayed around 2000 rpm and everything was fine. I checked fan belt which seems tight with about half inch movement when pushed however I can turn the fan which slips on the belt is that right? I took it up to speed but couldnt see any slipping.
Another thing to mention is the rev counter has been messing about recently, it jumped upto 4000rpm from 2500rpm without any change to throttle or speed. Not sure how the rev counter works and whether this may be a clue.

From what you say the Rev counter is electronic, correct?
So could be ignition/coil.
Also if the ignition timing is retarded it will run hot.
If you pm me with your email I can send you a link where you can download a full ford manual for the engine which tells you how to set the timing.

Did you check for an air lock in the rear cross tube?
If there is air in there the water may not flow properly through the heat exchangers.