MisterP said the following on 24/06/2007 15:35:
This is a 50 year old installation with existing vertical steel oval
conduits to sockets plastered into the walls. The rubber(!) cable
enters from above and there is a grommet inserted into each of the
conduits to prevent damage to the cables.

Now if rewired with PVC sheathed cable, then
a) Can I re-use the steel conduit?

Yes.

b) Where can I get suitable grommets? These are top hat shaped with
central hole for the cable.

Never seen 'em for sale anywhere. I'm not saying you will not be able to
get them; someone might come along and prove me wrong...

Just be careful when pulling the new cables through (use the old cables
to pull the new ones in).

c) The recessed steel boxes do not have an earth connection. Can one
be fitted or is it better to replace each box?

Better to replace each box - not least because the shiny new screws
supplied with your new accessories will be metric and the screw holes in
your old boxes will be imperial...