Hmmm. Well I went to Caravan Clinic and they said not only was the thermo-couple corroded, but also the burner itself was corroded badly and actually falling apart. They kept it out to show me and my guess is the water got in when I had that leak and over time has ruined the burner assembly. Never mind, at least it’s fixable. I asked how much and he said £150 +VAT for the part and then 2 hours of labour.
After I’d stopped laughing! I said I’ll check back next week. I made an appointment anyway, but set off to Camper NE to see what they said. They said exactly the same thing! Bloody hell it’s only a piece of copper!
Anyway I went online and ordered not just the burner but the thermo-couple and the igniter also as a complete kit for £38 from the excellent Leisure Shop Direct. I also ordered a new fridge door catch as mine had broken. Can’t wait to get some heating on.