If no calls made then no money is taken. Like you say there is a 4p connection charge (compare that to most other landline providers!).
I am confused by the 0p for landlines advert, because there charges table shows 1p/min.
I started my account with them in September 2006, last bill I had from them was February 2009, not used them since then and not charged a penny. Not once have I had to contact them about any problems, whereas every other telecomms company I have used have always had problems.
The answer is to try it, its online billing so you can check what it does, if you don't like it then just stop using it, there is no tie-in. The only problem is if your provider either blocks 18185's 0808 freephone number, or worse still charges for it.
If you have a BT line then you just prefix your calls with 18185 instead of using the 0808 number - you can register as many numbers as you want against your account eg mobile and home.
In a time of universal deceit - telling the truth is a revolutionary act. George Orwell
When the debate is lost, slander becomes the tool of the loser. Socrates