200tdi Defender thermostat

My 92 200tdi Defender has the original engine. Recently replaced the thermostat with a new one that was rated at 88 C. The engine is now running hotter than it always has previously. I’ve checked and some people are saying the 200tdi should have an 82 C thermostat yet other suppliers insist the 88 C one is correct. My understanding is the thermostats open at either 82 or 88 C but does this affect the running temperature? Once the thermostat has opened I’d have thought the engine coolant temperature would be cooled to the same temperature irrespective of the thermostat opening temperature. I have the original radiator & viscous coupling fan & not an after market electric one.

Yes, you are correct, the engine will run at the same temp but the 88C thermo will open slightly later than the 82C thermo.
Diesel engines like to be hot (around 100C) and need cooling (radiators, water jackets, pumps etc) so they don't get hot enough to damage themselves.
I run 88C thermos' too, my mate runs an 82.
No problems with either.