Here is a strange one. Started with a running toilet (just a small drip so didn't bother fixing) then noticed the water in the tank was warm... almost hot. Very strange.
Then I turned off the hot water to and from the HW tank.
Water still flows freely through the hot water taps in all the house, although it quickly turned cold.
I turned on the hot again and noticed that if you turn on the cold water tap close to the shower (with the Foremost mixer) the water runs quite hot for a second or two then cold.
Sooooo. I figure the foremost valve must be flowing between H and C. Take it apart. Looks OK but when you turn it on just a bit, warm water flows, on full(H) very hot flows.
Any suggestions??