Does anyone recognise this number?  It keeps coming up on my phone bill - only 0.06 seconds at the same time (usually 11.34 or thereabouts) but charges £0.17 each time.  Not a lot I know but annoying.  I tried dialing it with 141 before but just goes dead.

Just a random thought, are you by chance in Supported Accommodation with Life Line or some form of Emergency Aid call system, or have you had an alarm installed.

If either of these it could be the 'System Checking'

Sounds like a Burglar Alarm / Security System calling out as suggested.

The other possibility is if you have Sky its your Sky Box calling out but it shouldnt be doing it that often.