hall lighting, hall +landing both 2 way?

It should be fairly easy if there is enough space in the conduit.
You just need 3 live wires between the two switches connected to the same terminals at each end.
At the existing switch move the wire from COM to L2.

You may need a drop of liquid soap to help the wires slide down the conduit.

Adam
February 2010

Can I feed a cable down the existing conduit in the wall?

rosemary
February 2010

You wish to make the existing one-way downstairs light in the hall to be two-way switching. This will mean installing another lighting cable between the two switch stations.

You will need to install a two-gang switch upstairs and run lighting cable between the two switch positions. This may mean chasing out the existing cable channels so that you might add the new cable run - and make good - fill plaster decorate etc. Floorboards may aslo need to be lifted to route the new cable.

Is the effort worth the reward?

Good luck...

Peccavi
February 2010