Hi,
Even though HGF is a much rarer occurrenece on a KV6 - my advice for peace of mind is to fit a Hans Gauge - (On E-bay - MG ZT/Rover 75 EEzee Coolant gauge) - about £50 and 45 minutes for an auto sparks to fit. It shows the cars running temp and alarms at 110 AND 115 - saying that if your fan is working OK these temps will not reached. But you soon pick up the normal range of running temp for your car from the gauge - so you are forewarned if there is a coolant issue when normal parameters are breached.
You can also use the vehicles onboard diagnostic programme set up- AKA 19/07 - its a bit faffy but it will also display on your IPK the cars running temp as you are driving. If you search the site you will see guidance on the OB diagnostices which covers a lot of areas and i think for the age of the car is pretty good.
Others may recommend other solutions including just keeping a keen eye on the coolant tank contents but for me the Hans gauge is a really effective tool to counter overheating .