300 TDI cooling system/head gasket

Forgive me if I am going over old ground. I have had 300 TDI disco's for the past 10 years,two of them, both have broken down whilst towing the horse trailer with horses in causing a great deal of anguish ,the first overheated and seized ,and just yesterday the latest may have blown the head gasket.
My question ,how reliable at towing are these engines,is the cooling system up to the job when the weather is hot ( not southern England Hot ,I live in North East Scotland ).
I ask because as yet we haven't had the full story from the garage to which it was towed,but it has dented my confidence in disco's. I have heard stories of engines being prone to head gaskets going after failing once, due to stresses being left in the head ,even after skimming .
Any advice on ensuring it doesn't happen again ? Apart from the obvious, fan belt ,coolant level and rad hoses.
Do I get it fixed ,sell it and get a Landcruiser, Don't really want to I like the nimble well balanced feel of the disco. Or is there some way of getting the 300 engine up to Toyota levels of "bombproofness "
Cheers
LEE

300tdi is a good tow truck , engine only suffers from over heating if cooling system is low on coolant ,removing bung on thermostat housing and ensuring system is completely full is a must regulary , also rads fail , you need to feel rad all over its core and see it all gets hot commonly it doesnt and so is only partially cooling ,it is true if head has been too over heated it may go again quite quickly ,

radiator cooling fins have a nasty habit of turning to dust & totally losing
cooling efficiency . When i had overheating problems i found if i followed to close to a vehicle it would disturb the air flow & the temmp gauge would shoot up in seconds . my radiator was perfectly watertight but all the fins had disappeared hope this helps.