Privy Counsellors are "Right Honourable", rather than merely "Honourable". As one writer put it "The Privy Council was formerly a powerful institution, but its substantial decisions are now controlled by one of its committees, the Cabinet. The Council also performs judicial functions, which are for the most part delegated to the Judicial Committee."
The debate covers the history and activity of this "Council". Further information is available in a House of Commons Library paper at http://www.parliament.uk/commons/lib/research/briefings/snpc-3708.pdf - and the Privy Council website is http://www.privy-council.org.uk/output/page1.asp