PN home phone

[#1]

Several questions.
1.Can I ask anyone using PN home phone how the cost of calls compare against BTs revised cost of calls ? I Know the line rental is cheaper its a comparison of cost of local, weekend, evening, mobile and national calls I am interested in.
2. BT appear to be indicating that caller display will be charged for. Is this available from PN and does it cost extra ?
3. What happens if you are 3 months into a 12 month contract with PN on option 1 and you want to add PN home phone does the contract start again ?
4. I Thought BT owned Plusnet am I wrong in thinking this ?
5. Are there any disadvantages (i.e services unavailable to me,problems if my phone line goes wrong) if I have PN home phone against BT
I apologise in advance for such a string of questions but the horror stories from people who have changed services (not PN I hasten to add) and been faced with all sorts of problems is something I to avoid  for the sake of saving a few £s a year.
Thanks 

[#2]

1) PlusNet tariffs are listed on their website. I suggest that you yourself compare the ones that interest you with BT's. The call charges that I have checked have never been higher than BT's.
http://www.plus.net/support/home_phone/info/call_charges_guide.shtml
2) BT has always charged for Caller Display it's just the Privacy At Home option (that includes the equivalent of Caller Display) that is free provided one makes a minimum number of chargeable calls. Privacy At Home is not mentioned in BT's recent changes so I don't know what the position will be in the future.. PlusNet can provide Caller Display but always charges. See website for costs.
http://www.plus.net/residential/phonecalls/home/homephone_features.shtml
3) Unless taking advantage of special offers HomePhone is on a monthly contract and the problem doesn't arise. With a special offer I don't know.
4) BT owns PlusNet but PlusNet runs its own business with its own management and support staff, buying services from BT Wholesale, OpenReach etc in the same way that other ISPs and telephone service providers do.
5) PlusNet does not offer all the services that BT does. See website for the list of services it does provide. The most obvious omission is Call Barring. BT provides Premium Rate Call Barring free. PlusNet does not market Call Barring at all although barring of all calls to international &/or premium rate numbers can be requested at a monthly charge.
http://www.plus.net/residential/phonecalls/home/homephone_features.shtml