hi themostat stuck again, after 100 miles.
well its out, changed it this morning.
looks like it was sticking in closed postion after a hot run.
took it out for a spin seems ok.
may have to flush the system to get all the crap out.
once you free it up its ok , but will try again now with the new one.
cant really get in to have a look as its a sealed plastic bottle.

many thanks for all your help on the rebuild