By Naomi Rovnick LONDON (Reuters) -Some of Britain’s best known private equity-backed companies, including pub operator Punch Taverns and London City Airport, have been named by a buyout industry watchdog for not following its transparency and disclosure guidelines. The Private Equity Reporting Group on Thursday identified the companies as non-compliant with industry guidelines that urge timely reporting of how Britain’s largest privately-held businesses are faring financially. Buyout-backed companies in Britain make up a significant part of the corporate sector, supporting 2.2 million jobs an…