The work is to modify the lighting arrangements in a friends living room.
At present there are four wall lights and the plan is to remove these and at
each location extend the wiring down the wall (recessed) to a new socket
(round pin) just above the skirting for some free standing lamps.

I thought this would be peice of cake, I've just rewired my own house -
until I took the fittings off and saw the wiring arrangements.

The house was built around 1984.
There is a conventional, if old, Wylex consumer unit.
Ring main and power radial circuit cables are conventional twin and earth
(grey outer-old style) A photo of the interior of the box with cables and
some diagrams may be seen he
http://www.bluestar.65704.btinternet.co.uk/

The lighting circuit is something I had not encountered before.
it is not the conventional loopin system -or ISTM, the radial alternative.
The cables are all single, grey outer. Line (phase) red core plus earth
conductor, Neutral being single core black,

The lighting circuit is on one fuse. There are two line cables and two
neutral cables heading off, presumably a pair for each floor.

The arrangement appears to be that the line conductor is looped to each
switch in turn. The neutral cables are looped to each light fitting in
turn. A single cable (red inner) links each switch to its light fitting.

So at each switch there are three single red wires and at each lamp fitting
there are two blacks and a red. see diagram.

Presumably this arrangement makes for economy of cable.
I believe there are no hidden joint boxes anywhere (but I could be wrong..)

Question is...how to go about this job? (hopefully with access from the
floor above)
Can this type of single core cable still be obtained? I somehow doubt it.
So should the whole existing lighting circuit be replaced with a loop in
arrangement using twin and earth?
As the modifications required are only on the ground floor could this be
replaced with loop in and the upper floor be left as it is?

Please advise.

Roger R