These terms and conditions were last updated on: 30 June 2018.
Read Paragraph 6a.
You will find similar restrictions on residential accounts, with other providers, so I would recommend that you switch to a proper business product if you expect to get compensation in the future.
Here is the Customer Complaints Code of Practice, you may want to read how they deal with complaints, and ways to raise one.
I doubt you will get any compensation, you may get a reduction in the bill to the value of 12 days loss of Broadband and Phone.
Either way, any compensation would be very tiny and restricted to daily line rental credit.
The damage to your business if you get a default on your credit record, which will happen if you do not pay your bill, would be not worth the hassle.
Most faults are on the external network, which is provided and maintained by Openreach, which all providers, apart from Virgin Media, use. Changing providers is not going to make the service any more reliable, if they use Openreach.
As others have already said, if you want 'business' type levels of service , and compensation , you need to be on a business line tarrif, and if you weren't on that with BT, you doubtless with fail in any attempt to claim consequential loss, (over and above residential line compensation) after all you would have been running a business on a residential line.
If you are now using Sky's residential service, it's worth noting that they purchase a cheaper/slower level of repair service from Openreach, so with Sky , potentially it takes longer to repair lines as they pay less than BT to OR for their level of service.
If a fault occurred around the time you were switching providers, it's unfortunate, but the order to switch you , if you were migrating provider, rather than getting a new line , is entirely an exchange based operation and an existing line fault wouldn't affect that process, so in other words , if you were to be switched to Sky equipment in the exchange on a particular day , that would have taken place, irrespective of the fault condition on the line, the engineer who does the exchange work would not be aware of a fault report on the line he or she was moving, although it would complicate matters when you call for provider for an update , your old provider would see you were no longer a customer of theirs ,the fault report with OR from BT would still exist on the OR system .
Its an imperfective process, after all it's an unusual set of circumstances, which probably has no process to manage , but the 'fault' lies with Ofcom as they mandate that there is a separation between the end user and Openreach.
OR asked Ofcom for the ability to deal with faults independently of the service provider, but Sky and Talk Talk rejected the proposal , they want any communication with you, the end user to be via them, that is in part is why you have to speak to your provider when chasing a fault that OR are dealing with, you started a fault with one company and by the resolution of it, you were with another.
if the fault affected your neighbour's as well as yourself , then presumably , if they also reported the fault to their own providers , the OR repair that fixed their lines would have fixed yours to, even if you hadn't switched or even reported it faulty, and if your neighbour's were affected, it's unlikely that an exchange problem would affect them as well as yourself, so the problem almost certainly wasn't in the exchange but the local access network