The SHED has been overheating for a week or so which was causing it to cut out. We did a bit of googling and it looked like it may be the thermostat that was causing the issue. We purchased a new thermostat (£12) and set about replacing it, a simple job you would think but in the Rover 25 the thermostat and water pump are in a really difficult to reach place. After about two hours of work we finally had the thermostat out, a combination of one of us doing things from the top and another laid underneath reaching up. I am sure for someone who does this on a regular basis it can be done much quicker.
Once out we replaced it with our new one and set about trying to put it back in, this was even harder as the bolt fittings started spinning in their housing so we had to take it off twice to push the fittings back in. Then we had the problem of getting the thermostat back into the water pump, a lunch break appeared to give us a new lease of life and we used brute force to get it into the water pump.
Re-filled the system with water (no coolant, coolant is for girls) and started her up, ten minutes later and she was getting really hot and there were cooking noises coming from the engine block. A closer look showed water leaking out of the head gasket and this was boiling, not a good sign. A further google suggested this was really not good news and probably meant the head gasket was cooked.
Checks of Rover forums suggested that to fix the head gasket was going to cost about £400 and probably not something we could do ourselves. So the SHED was officially dead.