Thanks very much for replies, you've pretty much expressed what I was thinking but it's always nice to have it confirmed :D
I have contacted cotherm who are happy to supply me with stats in the future but wondered if anyone knows of an easier way to purchase ie: a local plumbing outlet?
On this cylinder are Two cotherm TSE thermostatically controlled immersion heaters.
The lower unit (economy seven) tripped it's internal reset, a few days later the same thing has occurred, so I lowered the temperature on the stat, but still the same problem occurs.
I have swapped the top and...