The flow from our BATH hot water tap is strange at the moment.--just a trickle with a small amount of turn, a decent flow at mid-way, then back to a trickle when fully open!!! (The bathroom sink hot flow is fine; as is the kitchen hot flow)---Washer or pressure? Any ideas anyone
Inside your tap there is a valve, it either sticking, want cleaning or replacing, it's not that hard a job to do Ken, you have to turn the feed off at your Hot Water tank, open the hot water tap in your bathroom sink / Bath.
Conventional (separate) taps on the baths rather than a mixer?
If so, then I agree it is probably the valve in the tap. Take off the handwheel; unscrew the shroud; then unscrew the valve from the body for a look. It might be no more than a duff, or loose washer.