From The Guardian  newspaper offers there is the following statement

Calls provided by BT will be charged at up to 8 pence per minute at all times.
A call set up fee of 3 pence per call applies to calls from residential lines.
Mobile and other providers costs may vary

What is a set up fee?

Previously BT charged a minimum fee, whatever the length of the call.
Now they charge a set up fee, as well as the per minute charge. That is a fee for setting up a successful call; success being defined as a billable call, i.e. completing to voicemail or an answer.
Have a look in www.call1899.co.uk (amongst others) for an illustration of a set up fee.

Note that this means that there is still a minimum charge for a connected call. That will be 3p plus 1 whole minute for geographical (01/02), mobile and international calls. All other calls are charged to the nearest second.

Dave wrote on Nov 5^th, 2006 at 6:08pm:

Note that this means that there is still a minimum charge for a connected call. That will be 3p plus 1 whole minute for geographical (01/02), mobile and international calls. All other calls are charged to the nearest second.

The minimum BT call fee in the weekday daytime is now effectively 6p instead of 5p made up of 3p connection and 3p for even 1 seconded rounded up to one minute.  A 20% prices rise.

Well done Ofcom. Another brilliant triumph of market forces benefiting the consumer I see.  ;) :o >:( :'( :'( :'(