As far as I can gather from experience here that there are no "plumbers", only handymen that think (that is too strong a word) they know what they are doing. An extension 4 years ago still has problems in the new bathrooms.
A recent upgrade of the original bathrooms led to water leaks in the wall (though this was probably due to the original construction) and a new vanity that is not secured to the wall so moves if I lean on it, and the tap (faucet for the Americans) twists when turning off and on.
In younger times I would have fixed all these things myself but as you noted the body is not what it used to be.