The bit we look at is "Every installation shall be divided into circuits, as necessary, to:
(i) avoid hazards and minimize inconvenience in the event of a fault
(ii) facilitate safe inspection, testing and maintenance (see also Section 537)
(iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit
(iv) reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents produced
by equipment in normal operation
(v) mitigate the effects of electromagnetic interferences (EMI)
(vi) prevent the indirect energizing of a circuit intended to be isolated.
It does not say power should not be taken for a supply used for lighting, and the electrician has to make a judgement as to if in your case he can use the lighting supply. Lighting is permitted less volt drop to power, but 55 watt is only the same as a bulb, so using a 2 amp or 5 amp three pin socket is likely an option.
As to
Lights are not on ring mains, they are radials.
well sockets are not technically on ring mains either, they are on ring finals, ring mains allow one to isolate part of the ring to work on it, but that can't happen with a ring final, but be it lamp or bulb, or any of the other places where it seems wrong term has been used, where it does not matter as it is clear what is meant can't see the point of correcting.
But more to point in the main the radial used from lighting goes from ceiling rose to ceiling rose, as direct as possible to reduce volt drop, and the switches often has no neutral, so unless your going to be fitting a projector in centre of the room it is unlikely there is a lighting supply near the wall. Many houses to again keep the run short are wired with two ring finals split side to side, it reduces the loop impedance done that way, so often the sockets are wired between the two floors, so except in a bedroom a socket supply is often as easy to reach to a lighting supply.
I would say some thing like this
means the electrician is not fitting a 13 amp socket to lighting circuit he is simply fitting a plug in ceiling rose, and if you plug the TV into this then that is up to you, he has not done anything which could be considered wrong, and it would not look wrong if in future you stopped using it.
