Hi.

I have had a small coolant leak for some time not from the usual places, so I decided to take things apart to investigate.

Here is what I found:

Previous owner had changed the clip on the thermostat outlet to a worm clip or also called a jubilee clip. The clip has been tightened to much deforming the outlet as you can see in picture 1.
This deformation also made a small gap between thermostat cover and water tower giving the leak. Picture 2.

Changed to aluminium water tower and thermostat cover which solved the problem.