No, but it has woken me up. We are in Bermondsey and it sounds like it is coming from East of us. Have checked the Environment Agency website and there are no flood warnings. Not sure what else to check.
Just called BBC London and switchboard said they have had lots of calls about it. There is a fire near the Blackwall Tunnel. Not sure what is down there that is so serious it qualifies for an air raid siren. Nothing yet on London Fire Brigade website.