Hmmm... I thought I had posted these to the database but maybe I didn't...
458.6625 DCS023 - Ushers/Security
453.4125 DCS023 - Operations
464.1375 DCS023 - Event Services
I also heard 469.7500 used during a concert (house lights on/off etc). Not sure if it's a JLC frequency or one that was being used by the crew that night.
For the events that have ISM Security in house, you will find them on 469.0625.
I just also noticed that if you look up those first 3 frequencies on TAFL they show as being licensed to London Civic Centre, so they may be in use there too. Both apparantly use the same management company (Global Spectrum).