...provided that the new cabling isn't buried (or suitably protected). I must say that I'm a little surprised by the implication that a house re-wrired in 2003 doesn't have RCD protection of its sockets circuits, aren't you?
Nothing surprises me any more, but I would have expect it to be there.
But I have seen rewires performed by the uneducated and ignorant, that even post requirements fall somewhat short.