bad shaver socket wiring?

[Baysboy]

Hi, hope someone can advise on the wiring of an existing bathroom shaver socket. I wanted to move this socket just 20mm higher to look better when I put some new tiles up, but discovered a couple of things which don't seem right. The shaver socket was installed as standard at the time the house was built by a well known national housebuilder in 1979.
The twin red, black and earth run directly from a ceiling rose, with the red and black going into the transformer type shaver socket, but with the earth only connected to the metal housing box set into the wall. There is an earth terminal on the shaver socket - should this also have been connected to the earth cable and metal box? The shaver socket does not have the double insulated twin boxes symbol.
Next, there is no supplementary bonding earth cable running from the socket to any piping. Should the socket have had this bonding?
I have a normal consumer unit, not RCD.
I am uneasy in leaving the wiring as it is having read other posts, but perhaps this was done to the regulations in 1979. I can "repair" the simple earth connection to the shaver socket and connect an earth bond cable to the nearest 15mm hot and cold supply pipes, but it would be too difficult to extend this bonding to the radiator pipes and bath pipes.

 

[TicklyT]

The CPC should terminate on the transformer rather than the back box. Maybe the transformer has been changed at some time, and the previous one was all plastic, without an earth terminal fitted?

Many (most?) would prefer to connect a flylead from the transformer to the backbox as well, but some (many?) consider the fixing screws adequately earth the backbox.

The circuit supplying the shaver socket may be bonded to the other services at another point. Bonding at every eletrical accessory and tap is not required.
Often supplementary bonding is connected to all the services at the point(s) they all enter a bathroom.

Additional bonding fitted without careful consideration of what may happen under fault conditions may render an installation LESS safe.

 

[sparkwright]

The shaver socket should have been directly connected to the earth wire, and a short earth wire from here to the back box. This is the best way to do it.

However, by earthing the back box there would be continuity through the fixing screws to the shaver socket terminal. By not fixing the faceplate to the back box would cause it to be unearthed.

Do you have other circuits in the bathroom besides lighting? Is there another point on the bathroom lighting where a bonding wire has been connected?

 

[Baysboy]

Thanks TicklyT and sparkwright. I can confirm that everything is original from when the house was built and there is nothing electrical in the bathroom other than a ceiling rose light and the shaver socket.
I am going to make the cable connection to the marked earth on the shaver socket now, with a short wire to the box too. As suggested it may well be that the 2 fixing screws through the shaver socket provide continuity but I think I'll play safe and not rely just on the fixing screws (in case different metal screws provide different levels of continuity).
The supplementary bonding is the issue it seems. Not sure where it could be being done as the bathroom ceiling rose is the first port of call in the lighting circuit after leaving the consumer unit . There is nothing there just the in-out cables, a switch cable and a cable to the shaver socket. There is bonding earth wire next to the consumer unit but I understand that to be primary bonding, not supplementary. But I think I am going to take your advice TickyT and not try any further bonding and trust in the original installation on that for the time being.
For the long term are RCD units reliable enough these days to have installed on this circuit as well as all my others? I understand supplementary bonding isn't an issue with such units, although it will be an expensive outlay for no particular reason if nothing is currently wrong.