Pull the water pump, see if it has a plastic impeller if it does replace the pump. Plastic impellers will fail and slip on the shaft and cause the pump not to work well enough to cool the engine. I see it in several makes including land rovers

 

Update: Borrowed thermal camera
Ran truck up to 210 F
Top of thermostat ~190 F
Bottom Cold
Radiator cold
Too bad I ordered a radiator yesterday ($60 ebay special)
Looks like I will order a 180F LR thermostat

 

Sorry Speedster, to answer your question the water pump had a metal impeller.

 

Was this an OEM 180F you have in there currently? Light Grey color? Or was it black 180F Britpart unit? I’ve had great sucess with both & have actually switched to using the britpart unit more vs the LR OEM 180F.

 

Update:
Borrowed a thermal camera
Ran the truck up to ~210 F
Top of thermostat ~160 F
Bottom of Thermostat and radiator cold.
Spoke with Lucky8
They gave me credit for the bad T-stat and shipped me a Genuine 180F today.
I had already ordered a $60 E-bay radiator.
I'll install it when the weather gets a little warmer and change to green AF at the same time.
Also purchased a $12 IR Temp gun-good tip, thanks.

 

Do you have the plastic t fitting with the bleeder over the alternator or the hose with the bleeder over the radiator?

 

The bad T-stat currently installed is an $18 All Makes P.O.S
180 F OEM on the way.
I have the plastic Tee with the bleeder screw on the truck

 

my 2001 disco 2 most likely needs HG replaced, i have made an appointment with BIGGS, WA but that is in 10 days from now. I had already bought a Low Temp T( i think, it is the black version) from Lucky8 so i installed it today ----- i am getting good at bleeding the circuit LOL
Temp now has gone down
from 210 running to 187-189 and idling from 226 to 202
i don't know what else to say ... the old T had 4 holes just as the new one. i did see something that looks like a very small piece of cotton cloth or so in the old thermostat
if anyone else is saying to me that their coolant temp is too high on their Disco then i say buy the low temp T not too expensive and on mine it was miraculous

 

Why do you say it needs the gaskets replaced?

 

If the motor is up to temp and the radiator is cold, there’s your answer.

Another thing is to check the fan clutch- if you rev the motor, the temp should drop.