I would be looking to see if the plumber claims to belong to a professional / trade association and be getting ready to contact them. He is clearly incompetent and doesn't appreciate what is expected.
With (domestic) Plumbers I believe there are many different types -
"Pipe fitters" - I wouldn't let them loose on fitting a bathroom.
"Bathroom Installers" - should be capable of recommending and fitting all the fixtures and doing tiling jobs.
"Central Heating Engineers" - as it implies. Capable of calculating radiator sizes and boiler ratings, etc as well as installing it all to CORGI regs.
I feel the whole spectrum is just too broad and speialist for one person to have the aptitude for all of it.
Any views?