Replacing ceiling-mounted light fitting in kitchen

A neighbour, who rents from a not-very-able landlord, has an aesthetically- broken light fitting screwed flush to her kitchen ceiling. She is unlikely to be able to find a matching like-for-like fitting in the shops, as the o riginal is at least 34 years old. The fitting is cylindrical, end to the c eiling, top half containing the works, bottom half being the side and end o f a short plastic diffuser - with a rather large broken hole in the end.
I judge the fitting to be rated at 60 W thermal; it currently has a same-sh ape LED bulb which feels to me to be about 5 W.
A replacement could be vaguely similar, or could be (OEM, & as I have) like the top of a traditional standard lamp. but the other-way up and batten-mo unting, similar to "MK Batten Lampholder Straight 1174RPWHI" on http://www. +Sockets/MK-Ceiling-Fittings/c/1000118; or to tish-general-batten-lamp-holder-white/93835.
I assume that there will not be enough cable to dangle, but that a unit lik e could be added.
Traditional UK BC socket preferred.
The work could be done by a reasonably skilled amateur (me), by the landlor d or his minion, or by a Proper Regs Part P (or whatever) electrician.
Suggestions / observations, preferably legal?

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