Thanks Steve, having had more of a closer look it does look like I also have coolant inside the v. So now need to find out what is leaking in there .

Hi I think you have solved it yourself as a broken bolt won't maintain uniform pressure on the gasket therefore water will escape. Steve.

Hi its obviously in its early stages, the reason it is slipping in higher gears is because of the torque load in higher gears, it used to be the old way of testing the clutch, find a nice hill and change up to early floor the throttle and if the clutch was good the engine would labour, if not it revved up, I would get it checked ASAP as when the clutch slips it creates a phenomenal increase in gearbox temps and cooks the rear crank seal which is a whole different story, having had it happen to me I can say its not a good day out. Steve.

Don. If you can smell the coolant it must be escaping somewhere, though at a mere 1500 miles per year the loss may be so small that you don't get a warning before the garage tops it up during annual servicing.

Thanks for the information which suggests that the old caliper was indeed at fault, even if nothing was visibly wrong with it.