O2 only very recently became owned by Virgin Media, and Virgin Media don't have cable service in my area.
The cell tower is on top of a big pole that comes out of the top of the street cabinet. Any environmental factors that affect my BT line are going to affect my O2 line as well.
Many years ago, O2 was spun out as a separate company from BT, previously they were known as BT Cellnet.
Orange, now one half of EE, now owned by BT was at one point owned by NTL who were one half of Virgin Media.
If you trace the corporate musical chairs of all the players in the market, you will find they are all linked to each other at one point or another.