Think its more to do with regional control. TiVO listings are split in to TV regions. You are in the London TV region, but there are 3 local channels operating now within in the London TV region area (& more are planned) that all use channel 159 on Virgin.
Cable customer since 1993. Services: FH TV, Sky Sports & Movies (2xV+), Talk Unlim Telco, VIVID 100, Virgin PAYG Mobile