Bit of a late update.
I didn't have the tools or equipment to get the rest of the bearing off, or out, and the stub axle was damaged, so took it to a local garage.
With the old bearing off, it was clear that the threaded stub was gouged, so the owner spent time trying to get me a new axle, but the lead time was too great. He did manage to get me a new bearing, which was shipped up from Taunton trailers to campbeltown, rather ironic that I live less than 20 miles from Taunton!
Anyway it looked like what trailer guy had said, the brake cable to that wheel had locked on, causing the grease to boil, and then destroy the bearing. So new cables all around.
No way to get a new axle, or stub axle, however they did manage to fit the new bearing and secure it in place with a castle nut, and a split pin, enough to get me home anyway.
Also went for new brakes on that axle.
All done just 2 days before I had to come back. Top job, and worked a treat all the way back to Zumerzet.
I can recommend Hamilton Bros in Campbeltown if you are up that way for sure, he got me out of a hole!
I will be ordering a new axle soon, and then I will have 2 spare hubs, and bearings in case I have the same again.
Plus I have written 100 lines
"I will make sure the brake cables are greased every 6 months!"