"Garibaldi8" wrote
| The problem is, there are three twin-core-and-earth cables entering
| the current ceiling rose, and two much smaller red-sleeved cables.
| It appears that the red-sleeved cables are running to switches (two
| switches operate this light) but I was not expecting to find three
| other cables - just two, if it is a loop-in circuit.

Although the normal way of wiring 2-way switches is to go to the first
switch in Twin&E (as for a one-way switch) and from the first to the second
switch in Triple&E, it is quite permissible to run Triple&E from the rose to
*each* switch. In this case, Twin&E plus a single have been used instead of
Triple&E, which is also not unusual.

You can check this by looking inside the switches.

The third Twin&E is the supply in.

The red-sleeved cables should be red insulated with an outer grey or white
sheathing.

You can replace the ceiling rose with a junction box above the ceiling and
run 1 Twin&E to the location of the new light, although as Set Square says,
the other half of the hallway may be a bit dark. You may need to use choc
blocks for some of the connections (*inside* the junction box) as I make it
that 6 terms (incl the earth) will be required). A deep surface pattress box
with blanking plate may provide more space than a typical 5A junction box.

Just label *every* wire carefully. Earth not shown below.


----Neutral In-------------------------------------O
|
----Live In---------------O O-----------| O---| |
| | O-----| | | | |
| | | | | | | |
| | | | | | | |
| | | | | | Lamp
| | | | | |
Com L1 L2 L2 L1 Com

Switch 1 Switch 2




Owain