Hi Jaki
You can also obtain them from the General register office (GRO). Their web page has more info
http://www.statistics.gov.uk/registration/general_register.aspunfortunately being from overseas you wont be able to order them using their new online service.
It will cost you more through GRO than through the local register offices £8.50 sterling as opposed to £7.50 at the local office (well it is at mine anyway I don't know if they vary their charges). The only advantage with the general register office I have found is that they accept credit cards which some of the smaller local offices don't.
The certificates from GRO seem to be computer printed onto a certificate from a scan of the records whereas from my local register office they are a handwritten copy made by the clerks and are a lot easier to read. I know I'm probably strange but the handwritten certificates also seem more authentic to me and have more a feel of the past.
Told you I was strange!
For me I'd use the local offices wherever possible but as they say. The choice is yours