Ofcom Telephone Number classification

Many people are not sure what sort of cost group particular numbers are. This may help as a high level view: Especially take note of the new 03 range introduced by many health centres from Jan 2007 - these are local rate costed numbers but not geographically fixed. Hence like a lower cost 0845 number.

National Telephone Numbering Plan

		Area codes
		UK-wide numbers
		For future use
		Reserved for personalised numbers
		Mobile numbers (note: not 070 which are currently used for personal numbers)
		Freephone
		Business rate services
		Premium rate services

* 03 numbers became available to use from early 2007. They cost the same amount wherever the caller is located. Service providers like government bodies and financial organisations may choose to use these numbers instead of 08 business rate services numbers such as those beginning ‘0870’.

The price of calls for each number type varies between different providers, including between landline ('fixed') and mobile companies. Ofcom is currently reviewing how to let callers know more about call costs from the number dialled.

Source:
http://www.ofcom.org.uk/consumeradvice/landline/adviceno/