I live on Snowsfields and keep being woken up during the early hours, between 1-3am by some kind of two tone alarm/siren - similar to the alarms you get in office buildings. It lasts for a few minutes (but of course I can't get back to sleep for a while after)
I am pretty sensitive to sound, but I'm pretty sure I'm not the only one hearing this/being woken up by it. I thought it might be something to do with testing of equipment at the station perhaps. Has anyone else been disturbed by it?
I've also heard what sounds like the alarm you describe in the early hours, accompanied with a recorded voice but it's not possible to make out what is being said. I once walked past HMS Belfast and heard it emit a very similar alarm so have assumed that was the source.
That's the alarm in William Hill on the corner of Snowsfields and Weston Street. You can report this to Southwark Council Noise Team. They have powers to take enforcement action.
Go to www.southwark.gov.uk and search for "noise".