Understanding 'credit'

[#1]

As someone who's switched to PN Home Phone from BT as of today, I'm a bit confused. Obviously I'm used to a system where basically you just run up bills to your hearts content and then pay them off quarterly in arrears. Now I'm having to get used to something a bit more restricted, and this is involving a bit of reading between the lines in the explanations. So am I right in thinking...
I have a nominal 'credit' of £50 a month, meaning that as long as I stay under this, I can use the phone as normal, but if I am going to go over that, I should 'add' some more up front, or risk not being able to call out, and paying a few quid penalty to get going again?
Also, I'm a bit confused by the 'Current balance' figure on my Account summary. As of signing up, it reads £0.00, and clicking the details button next to it takes me to a screen that says 'Credit is required to make calls which are not covered by inclusive minutes to UK landlines e.g. mobile and international calls.'. Does that mean that even though I haven't used any of my £50 standard credit, I still have to add some more to ring my first mobile number? And if so, how come I got straight through to one without doing so? Will that have counted as 'going over' and incurred my first penalty charge?
I don't mind having to plan ahead a bit, but I need the terms spelling out for me!
Hope someone who knows what's going on can help.
cheers

[#2]

Perhaps this earlier thread will help.
http://community.plus.net/forum/index.php/topic,61243.0.html
Also
http://www.plus.net/support/home_phone/info/billing_guide.shtml#5

[#3]

@ lowden
If you go to Phone Calls/My Account you'll see a link "How we manage your credit limit" at bottom of account summary on RHS.
Calls are added to Current Balance once confirmed - prior to confirmation the 4.5p set-up fee isn't included.
Unless you're a very heavy user, who spends over £50 a month on calls, you've nothing to panic about.

[#4]

Also, of course, you can add credit which is what I do to cover the cost of additional calls such as mobile and 0845/0870 numbers.
Although being in credit is not everyone's cup of tea, you have the security of knowing you are covered and the bill at the end of the month is always the same.
It is under Account summary/Current Balance/Details - it's added in multiples of £5 and taken from the named bank account.

[#5]

that depends on how you pay, with my home phone the items are shown as a charge and are added to my direct debit
first pic normal
second with extras
the £50 is a ceiling to your extra charged calls

[#6]

OK, I thought I understood the 'Current balance' part - basically as I make chargeable daytime calls it drops from £0.00 until it gets to -£50.00 at which point I have to add credit, but I'm still confused about the mobile and international part. Do I have to add credit before I make those - the text 'Credit is required to make calls which are not covered by inclusive minutes to UK landlines e.g. mobile and international calls'?
If so, I don't understand how they are different from other types of chargeable calls, like daytime landline ones.
I supposed it comes down to what 'Credit is required' means. Does it mean 'Current balance must be > £0.00', or 'Current balance must be > -£50.00'.

[#7]

No need to add credit provided you've not spent £50 on calls not included in basic package - eg mobile, International, 0845 & 0870.
As suggested you can add credit as you go should you feel happier that way.

[#8]

Cheers! Now I get it!