I've taken the oil thermostat out this afternoon.
Cleaned it up and tested it.
Didn't have to warm it for long and it opened up. Obviously, I was hoping it wouldn't.
On refitting the thermostat and it's spring back in to the housing I realised how strong the spring is, so I suppose there is a slim chance that the stat might be able to open, but is no longer strong enough to open against the spring? Think I'm clutching at straws there.
The spring was that strong I couldn't push the housing down on the spring and get the bolt in at the same time. Space is tight/awkward, so used a spanner up against the inner wing to compress the spring and hold the housing in far enough to get a few threads on the bolt started.
View attachment 196840
An aftermarket stat is about £6 and an OEM one about £40 I might as well order an OEM one and fit it after new year.