if the cable does not have a separate earth cable it must be R.C.D. protected as per the 17th edition.(it should not have a separate earth because that was the system of protection under the 16th edition). the bathroom is considered a "special location" and has different rules compared to the rest of the property i.e. no sockets (please do not come back with a comment about the 3metre rule).
on the points of technique you mentione,d the outer grey insulation must be taken into a fitting/consumer unit when terminating and it is not safe to tuck a cable under the carpet or to have it exposed.
to give you an idea of the potential harm you face i recently had an inspect and test on my new extension that also included my 10 year test on the rest of the property and i know i have a 60 A service fuse. i expressed concern about this to the spark, a mate and he measured all my electrical load. everything in the house at once, the whole lot. out of a 83A full load ,a 9.5 kw shower was pulling nearly 40A.the biggest single item so please do not take any chances with your installation
ask him about your concerns and don,t be put off (try not to lose your temper).if he cant prove that what he has done is safe, tell him you will report him to the building control/trading standards/watchdog whatever, and try to get your money back because i think you will be paying another electrician soon, if only for peace of mind