PN Phone & Broadband.

[#1]

Currently have a BT phone package which ends in November.
If I switch to one of the deals with PN for phone & Broadband exactly what changes (apart from conditions and price)
What I am really asking is what happens if any problem occurs with my phone line who do I contact ? If it's PN  am I likely to get the same level of service to sort the problem as the service I could expect from BT. ?
Also are there any known disadvantages in changing from BT to PN ?
Are there any other things I should be aware of that are not covered on the PN pages that give detailed information about the various phone & Broadband packages currently on offer ? 

[#2]

PN doesn't offer all the optional phone services that BT does (e.g. barring calls to specified numbers or to mobiles) and charges 99p per month for Caller Display which can be free from BT (subject to certain conditions).

[#3]

@OP  Yes, phone faults would be reported to PN if you're paying line rental to them. In theory, BT Openreach should handle all line faults equally under Ofcom's rules re equivalence. I've not had occasion to put this to the test.
Do you make any international calls? When I transferred from BT to PN Homephone last year, on the Anytime package, it included 300 International Minutes - useful as I call Ireland and New Zealand. That is no longer the case for new sign-ups - it's now 25 per cent discount on fairly high international charges, so I wouldn't be tempted now.

[#4]

I've just swapped our phone line from BT to +Net and, the broadband  without any problems. Just make sure if you are thinking of leaving BT that you contact them and tell them you don't want your call package contract to continue after November . If it's an annual contract which is renewed automatically after that date you will get charged for terminating your contract like I did (about 30 odd pounds)