The new thermostat is branded Quinton Hazell, is anyone aware of their reputation? (Good or bad!)

Used their stuff for years.

Never had a problem with them.

Did you clean both faces thoroughly before making the joint ?

>> But the drips coming out the bottom don't lie...

Oh yes they do!

I swapped a thermostat recently on my car and also had what appeared to be a gasket leak. A turn on the hose clip attached to it sorted the issue. The coolant was weeping from the underside of the hose, running down the thermostat housing and dripping off the bottom, looking for all the world like a leaking gasket joint.

I have a 1.9 diesel DW8 van (year 2000), and mines been leaking from the thermostat cover for some years.

A new cover is £10 on ebay, I might be purchasing one.

This is one cover that needs to be made out of metal though , NOT plastic, its just rediculous.

I think what happens is the bits where the 3 bolts go through, distort over time.Then when the cover is disturbed and refitted, the bolts arent able to exert enough pressure on the three "webs", hence why I prob' might try a new cover .My leak is far worse than yours....