I found this thread diagnosing an overheat issue with my Britannia range, ceramic hob version.
It’s a 2009 model but we’ve had it 3 years. Like yours, it has always been prone to tripping if the fan oven was set over 220c. Clock turns off, after five minutes reset and carry on. I wonder whether the fan sensor needs moving, like yours.
However – I thought I’d add here for future Google searchers – last week it started tripping much lower – below 100. Bit inconvenient ..
I took the overheat stat off (two screws to remove the back panel that side, stat on top corner), tested it with a multimeter and it only took a little bit of heat to trip it, definitely not the 140c it’s rated for. So I swapped it with the one from the non-fan oven (it’s in the middle of that oven’s back panel, where the fan would be if it had one). All working good, dinner saved, and I’ll order a replacement. Both ovens have a Campini TY60 rated at 140 degrees. Wonder if they get more sensitive with age.