I'm talking about switching your phone / internet provider. Unlike gas and electric which you can switch at will, what I've found out is that if you move your phone away from BT, you're on a very sticky wicket if you ever want to move your broadband away from the LLU you've got your phone with. In summary, it appears the only route for your phone line, initially at least is back to BT. Then your chosen ISP will not be able to take your order until the phone is both BT, then there'll be a two week delay while they get you on line. In other words, you're without broadband for quite a period.
So, have ordered a new line and broadband with my chosen provider, then will cancel the existing setup with Sky. I get to have internet without interruption, but will have a new number (no bad thing given the amount of junk calls I get despite being registered with TPS)
So, think long and hard before moving your line away from BT, if you do, expect a period of darkness if you want away from your none BT provider).