Hey. Thanks very much for the reply and the link / photo.
I had seen the Brickwerks unit and understand that the 80deg one is better than the 87 deg standard unit. However, all this was gleened after I bought and replaced the current tstat (typical, eh!!)
So, this is the one I took out. It doesn't seem to have a part number but is 'Wahler - West Germany' It also has '87' stamped on the bottom as well as '4/3' (not sure what that might signify?)
I didn't take a photo of the one i put back in but this is the box. It came from a motor factor online who ask for all vehicle details before showing products. The only discernable different was the seal fitting around the rim rather than on top of it afterwards.
I did test the original tstat I took out in a pan of boiling water and it did seem to work so I'm still unsure if this was the probelm anyway??