I currently have sky multiroom package and my Broadband and landline with BT. I have two lines in the house so have separate BT Broadband accounts for each.

I am looking to change this and get a sky, phone and broadband package, but would I be able to do this with both telephone numbers? Would I still need to get a separate broadband set up for the other telephone number?

I am facing exactly the same decision! I also have sky multiroom with 2 phone lines and 2 separate broadband hubs which are all with BT. I contacted Sky and asked that if I go for the whole package would I still be able to use one of my BT broadband hubs on one of my lines, i.e. both talk line rentals from SKY, one line working on SKY max broadband and one remaining with BT broadband. The answer I got was yes, however I am not yet convinced and reluctant to risk it. After all, they are only selling it and don't have to live with any issues I get later. Our BT business hub is employer provided but I am prepared to change our domestic one. I will look out for further posts on your thread with great interest.
It seems technically possible, but there are so many other factors to consider.......
I have read so many horror stories about switching broadband provider that seem to outweigh the positive ones that I am becoming paranoid about changing it. My wireless reliability is excellent, the hub works perfectly so there is a strong voice in my head saying why fix something that isn't broken?
The motivation is -£2.50 / month saving on each line rental and -£13 / month on broadband (if I get the SKY max service discounted to £10/month by ordering together with the line rental. In summary for a potential saving of £18/month I get a lot of potential risk, not least of which if SKY increases prices, (as they surely will), I am back to square one!
Good luck!

You have to consider each line as seperate enitities therefore you can do whatever you like with each. There's nothing special about BT broadband, any ISP will work.

Flexible: As for not fixing things that are broken, can sympathise having gone through about 5 ISPs in 5 years.

Is Sky max is available on your exchange http://www.samknows.com/broadband/search.php

If not it's just Sky connect you can get.

Check the Ofcom Classification of your exchange on that Samknows Exchange search. If you are Market 3 there's a good chance that you can get a better deal from BT when you ask for your MAC so you can keep your existing service cheaper than you have at present.