Utility Warehouse just offers things, they don't have anything theirselfs.
You could call them retailers/resellers.
Talk Talk Telecom is part of British Telecom.
Utility Warehouse is buying network services from BT (Talk Talk Telecom) and than sells it to consumers.
mnashp,
it is not a issue.
Just a matter that most consumers don't know how things are working.
Try to imagine this:
Each "provider" has its own network.
Think about how many cables there must be in the streets/to your house.
Get the picture?
Hundreds of cables coming into your house so you can choose the provider you want.