stumpey,
Thanks.
In answer to the second half of your post, it's all a bit complicated but I'll try to help.
Until LLU (Local Loop Unbundling) was introduced in 2004, all copper cabling was monopolised by BT. Technically, now post-2004, the cables remain under the BT monopoly (although supposedly under their "independent" BTOpenreach division). But what has happened is that other operators have now been permitted to place their equipment in the local BT exchanges (at a cost, of course !) and hence be able to provide "independent" services. Due to rise in automation in the BT exchanges, the MAC code therefore speeds up various automated processes.
There's no LLU on cable plant.
Now, if you're a VMB (Virgin Media Business) customer there are a few extra tricks you can use to get your internet connection through another provider over the Virgin system. But then you also get the benefit of an account manager, access to the lovely "complex provide" team and a contractually guaranteed 4 hour fix time...
Feel free to fire away if you've got more questions or if I have not answered your question .....and I'll do my best to clarify.