Quote:

To be fair (it's not often I am where BT is concerned but sometimes they deserve a little leeway) BT's 5p minimum call charge is just that - a minimum charge for a call, NOT an additional connection charge.

For example, a 1 minute call to an '01' number during the day on BT does, indeed, cost 5p (because the per minute charge is 3p and the minimum call charge of 5p is greater).  

However, a 2 minute call to the same number costs 6p (2 x 3p) because the 5p minimum call charge has been exceeded.