baxi boiler pilot light

Hi everybody.
I have a baxi boston boiler that cuts out after a few mins . The pilot light will stay on for hours if the main burner is not on .
I have cleaned the burner/jets/everything else i can see.
I have fitted a new thermocouple.
When it cuts out the thermocouple is still glowing red hot.
It used to do this about once a year but a new thermocouple used to fix it but has'nt this time.
Any ideas suggestions please.
Please help Im freezing...

gas valve?

Duff thermocouple ?

Just because it's new doesn't necessarily mean it's OK

A job for Corgi eng to check burner pressure and possible black dust blockage. Gas supply to pilot may be starved when main burner fires up.