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?
b) Where can I get suitable grommets? These are top hat shaped with central hole for the cable.
c) The recessed steel boxes do not have an earth connection. Can one be fitted or is it better to replace each box?

Many thanks.