I agree with many of the comments above, but can possibly add a little from my own experience.
The later versions of the Rover V8 were designed to run very hot in order to minimise emissions, so the margin between "normal" and too hot is much reduced.
What pressure cap you have on the remote expansion tank? Check that the rubber is not in poor condition. A 13 psi cap will elevate the boiling point to well over 100 Deg C. There should be no pressure cap on the radiator itself.
As Mick says, is the gauge showing temperatures of over 100 , or is it actually boiling and forcing coolant out through the reservoir overflow pipe. As per Bruce the Morgan gauges are highly inaccurate and may be reading well over (or under), usually depending upon the quality of the earth. An indicated temperature of 110 is not normally anything to worry about.
Is the electric fan wired up the right way around ? If in front of the radiator you need a "pusher" , and conversely behind the radiator you need a "puller" Easy to get the wires reversed and on some motors this will result in the motion being the opposite of the desired one.
The oil cooler should help reduce coolant heating by conducting heat away from the engine. A larger ali radiator is a very sound investment , but not cheap , the bonnet bleed brackets will also help a little.
