thought i'd share with you all my latest "upgrade" After a bit of thinking and research i ended up using a BMW in line stat. biggest prob was finding a 32mm T piece, ended up at an aquarium suppliers!
fitted it today, halfords still do flexi hose :-) It all works as well,phew! One query, the temp gauge on occassions goes from 80 to 110 in about a minute then back again in about 10 secs, the fan doesn't alweays kick in so the water isn't that hot, could it be an air bubble by the sensor? it did this a year ago then stopped, i'm hoping it will settle down.
Chas

Sounds good. Your problem sounds like an air lock somewhere.

The temperature fluctuations sounds like a by-pass issue.

Source of 32 mm tees = Rover 75 1.8 (other 75s engine types too and I am pretty sure and late MGTF ) -- also handy 32 joiners which can be found on just about just about any late 90s Rover.

Just before the axe fell Rover switched to a variation on the BMW inline thermostat called PRT, that opens on presure as well as temperature, this was a very effective tweek.