This site is fantastic to find telephone numbers. You simply click 'search to find alternative number', type in the name of the company you are phoning and it will come up with either an 0800 number or a number with an area code.
Not all numbers are there but as yet I've not been let down!
I have recently spent a lot of time on the phone to O2 and this site gave me their 0800 number!
I hope this is of use to some or you. Debs