I found this some moons ago, but it had a very strict Copyright (i.e. you can only use it privately)
Has that changed?
I guess it has changed as the post I made was shortly after some kind of relaunch. (Not 100% certain though as I haven't used it myself, but they seemed to be touting the "free" aspect.)
Checking the detail at the top of the page it states: "These 16,000 BBC Sound Effects are made available by the BBC in WAV format to download for use under the terms of the RemArc Licence. The Sound Effects are BBC copyright, but they may be used for personal, educational or research purposes, as detailed in the license."
Having a squiz through the RemArc Licence, it is fairly liberal, with rather reasonable conditions of use. I'm left thinking that if you are using them for advertising, television, movies or any other sort of commercial use, it's best to use the contact email to enquire just how "free" the samples are for you to use.