More information from the British Red Cross:
Outside the UK
British nationals overseas should contact their nearest British Embassy or High Commission.
Other nationals overseas should contact their respective Ministry of Foreign Affairs or Embassy.
Those who are unable to do this should contact their local National Society (Red Cross/Red Crescent) tracing services (see http://www.ifrc.org/address/directory.asp) who can forward their request to British Red Cross international tracing and message service.
More from the Australian Red Cross:
Australians in London
Those who are concerned about Australian relatives in London during the incident should contact the Department of Foreign Affairs and Trade (DFAT). DFAT has responsibility for Australian citizens travelling or living abroad.
DFAT Hotline.: 1800 002 214
website: www.dfat.gov.au
Non-Australians in London
Those who are concerned about a non-Australian relative in London during the incident can initiate a disaster tracing request by contacting the Red Cross Office in your State or Territory and asking to speak to a Tracing Officer. State and Territory contact details can be found on the Contact Us page.
The Tracing Officer will assist you in completing a disaster tracing request which will be forwarded to the British Red Cross.
To assist us in expediting your request, please ensure you have the following information:
* full name of missing person
* relationship to the missing person (we can only take requests for close relatives)
* home and work address and phone number of your relative in London or elsewhere in UK
* the last contact you had with your relative and by what means
* reasons why you believe your relative was in London during the incident
* attempts you have made to contact your relative since the incident
Useful Links:
British Red Cross Society website - information for missing relatives