Another update.
Fitted new hose. Back flushed heater matrix as advised. Lots of burping through the expansion tank. As the coolant got to the top I put the heater matrix hose back on and topped up with concentrated antifreeze to strengthen the mixture up again.
Started up, ran about 2000 rpm with cap off, topped up, burped hoses.
Top hose was warm but temp gauge shows not halfway yet, so not sure if thermostat was open. Temp gun shows hoses at 50 degrees but rad at 15-19 degrees.
Left it cool, topped up and repeated above.
Hose temps now at 60 degrees and rad still the same. Temp gauge still not at half way.
Rad bleed hose is leaking out coolant when removed from rad.
Can I just presume the stat had not opened yet? 60 degrees is not enough, should be 80-90 degrees?
Loads of heat at the heater with blowers on full. The bypass hose I replaced is 65+ degrees, as it the hose to the heater matrix. Return it 50+ degrees.
Then I noticed it is still dripping from the LH side of the rad around the stat.
Dark now so I need to check again when I have the chance.