My hot water tap will turn off and on but it keeps
Slipping ie when I turn it off or on the twisting motion
Of doing this makes the entire tap no longer
Facing forward like the positioning of the other (cold)
Tap. It appears to be on a black rubber or plastic
'Thing'. I've tried to tighten what I think is the
Nut under the sink but it feels fully tightened. Please
Help!!!!

Leone, August 2015

If the body of the tap rotates as you turn the tap on and off it will be due to a slack nut underneath - it will need to be tightened - hold the tap in position and use a special spanner to tighten up underneath.

Basin Wrench - Amazon under £10
DIY supermarket

Good Luck..., August 2015