Hot water tap stiff to turn on and off?

don't know the make of the tap I've got but its a mixer with knobs like the house taps with colour rings blue cold red hot these centre caps pop out to reveal the screw that hold the knob on the tap shaft. Spanner needs to fit snug on the nut tap centre (adjustable spanner ) Hold the tap body turn the tap anti clockwise to release it remove the tap centre, caravan shop may have replacement or even a plumbing shop. If not replace the rubber washer, first clean off any lime deposits put Vaseline(petroleum jelly) around tap centre moving part. Ensure it moves free then reassemble the tap. Did mine work ok now. Don't know why the hot goes tight but same problem with one in the bathroom in bungalow.

Bob UK
October 2013