Hi Paul, good to know you have got on top of these problems.
Pretty normal trials and tribulations for the car builder I'd say.
No matter how much planning and thought you do at the build stage there are still problems which road use shows up.
There is some debate about the need for a thermostat at all if you fit the Davies Craig complete with controller.
The initial slow/intermittent running is to allow quick warm up even without a thermostat.