I have and have had MANY British built motor cars. One thing that THEY all have in common, other than the Prince of Darkness is Temp gauges that DO NOT WORK;
Rovers: If the dash gauge is above the center it is overheating and no one trusts them.
Jaguar V12 XJS same as above about the middle of the scale is 220 deg.
Rolls Royce they have a RUBBER BAND I THINK the temp SLOWLY approaches the warm the BOOM HOT.
This is just an observation after having so many of them with the GEE I HAVE NO IDEA Temp Gauge.
UG is the answer where it can be used but the older cars are another think all together.
Lost an engine in the P38 to overheating that dropped a liner, 1995 D1 same deal. The 2000 D2 needs a radiator and water pump. 2003 D2 is fine on temp just needs the exhaust gasket replaced.
Have fun

 

I've replaced exhaust gaskets twice, they're gone again. This time I said screw it and ordered a welder. My y-pipe is botched to sh*t right now anyway so I'm just doing headers and re-doing exhaust all the way back with a cat-delete and larger diameter pipe. 2.5" y-pipe to 3" single out the back with mandrel bends instead of crush bends and v-band clamps all around.

As for the temp gauges, I think that that's pretty much true for all modern vehicles that don't have the actual numerical temperatures marked in my experience; not just english vehicles. I doubt I'll ever own a vehicle without an aftermarket gauge of some kind.