BT Number Presentation Service
We can arrange for your 0800, 0845, 0844, 0207 or indeed any of our numbers to display your national number when you make outgoing calls. This is also known as your caller id (CLI). Alternitively, you can do it with BT using BT's Number Presentation Service. Every time you make a phone call your 0845 or 0800 number will be released as your CLI. (rather than your local area number, or a withheld number.)
If the person you are calling has caller display then your marketing number (e.g. 08000 484828) will appear on their telephone. Also if the person you have called dials 1471 then your marketing number will be listed.
BT currently charge £60 to set this service up plus £6.95 per quarter for maintenance. For further details call BT directly on freephone 0800 328 8883, or download their application form in pdf format.