Pendleton is still alive, but ceased being involved with the Marquee back in 1988.
http://www.themarqueeclub.net/harold-pendletonThe last Marquee closed in 2008, but a new club 'Marquee Live', with Pendleton's blessing, opened in January 2011 at the Monarch in Camden's Chalk Farm Road.
http://www.themarqueeclub.co.uk/Coincidentally, it's just a short distance from the London Roundhouse, which re-opened about 5 years ago and which was where the Stones played the final dates of their 'Farewell Britain' 1971 tour just 12 days before they taped their TV special at the Marquee (they havent performed at either venue since then). The Roundhouse has more recently been known for hosting the 'Electric Proms' series of concerts and it's where Amy Winehouse made her last public appearance in July just two days before she died.
Pendleton always hated the Stones and thought they were crap. He fired them from the Marquee and whilst the 'banner' incident at their 1971 return appearance at the venue caused a lot of dispute, the incident which reportedly 'triggered' Keith's violent reaction was him overhearing Pendleton at the rehearsal dismissing them as being 'the same old rubbish'.