I noticed during Derren Brown's "Control The Nation" show that the number he gave out for people to call in on (03457 224500) was indicated as costing something like 7p a minute with an 8p connection charge.

I was under the impression 03457 calls were included in any call packages the customer might have, and billed as per a call to an 01/02 number?

Yes, 03 numbers (whether 0300, 0330, 0345 or 0370) are all supposed to be charged at the same rate as 01/02 numbers. Considering it is obviously an 0845 migrated number, I can only assume someone thought it was charged at the same price as 0845 number, hence the incorrect pricing information.

Sounds to me like the pricing information has been left from when it was 0845.

The cost of calling the number is dependent on the price the caller's provider charges. It is common to see rates quoted either the maximum price from landlines (assuming the figure is correct, i.e. they checked with all landline providers) or more often the maximum price from a BT line.

The cost of calling is not dependent on what the production company decides, contrary to what Mr Brown may try and make you believe!