10 miles since a re-build eh, couold it be airlocked, iI dont know if this can happen but if so will render the cooling useless and have the net result you say. Vez i'm not doubting what you say about the elevated boiling point, with a 50/50 water antifreeze mix the BP would be something like 135C, this will be further increased when you take into account pressurisation. In hindsight it may have been unwise to say what I did, since this was not a 'can i use it in emergency ?' case.
BUT, knowing how COOL my bike runs .........