Please can someone tell me what numbers (ie: Dialling Codes and stuff) you would need to put in front of a London phone number if I were to call from the USA?

Number could be (020) 8123 4567.

Thanks Alot.

+44 20 8123 4567 (I think)

This site is pretty good, it will tell you easily what number to call

http://www.countrycallingcodes.com/

Thanks for the link! Is it just the USA that has a different prefix (011) as the only countries I've ever had to phone the UK from have "00" for international calls. (Admittedly they were all in Europe)

Thanks alot everyone!

Most countires do use 00 though there are a few exceptions, the USA being one, and other countries formally part of the USSR for Example Belarus where you have to dial 810 for International access.

Cheers Ollie!

From Australia 0011.

We in Europe harmonised our international code.

The good thing with calling from a mobile, you can use the + sign, as in +44207432nnnn, the bad things about using a mobile, the very high cost.