Nick:
Postal counties still exist and are maintained, they just aren't one
of the
mandatory address fields. However, as far as I am aware, the RM
*still*
recommend the use of the postal county for places such as "Rainham,
Essex"
and "Rainham, Kent" to avoid any potential confusion.

[sorry if the formatting's screwed - googlegroups confuses me]

Just as an aside, National Rail refer to them as Rainham, London and
Rainham, Kent...

Jonn