Hmmm, I would have thought that if a kettle or radio lead fell into a
metal kitchen sink it would be better off if it was earthed.

I'd still prefer insulated and with all sockets on an RCD. Even if the
non-earthed sink doesn't provide sufficient earth leakage to blow the RCD,
it is easy enough to just turn off the appliance before retrieval.

Besides, you should be using kettle leads. It is much safer to use a
cordless kettle with a short lead to the base that won't even reach the
sink.

Christian.