There is no regulatory body for airlines, as such (but see below for details of the 'watchdog' for the industry).
However, you have certain rights relating to compensation for delayed or cancelled flights departing from any EU airport or operated by an airline registered within the EU (such as BA), even if the flights are outside of the EU. Full details are here:
http://ec.europa.eu/transport/air_portal/passe nger_rights/doc/2007/com_2007_0168_en.pdf
If that looks rather complicated, you can phone 00 800 6 7 8 9 10 11 (free of charge from landlines, from anywhere in the EU) from 0800 to 1730 GMT, Monday to Friday, for advice on your rights.
If you believe that your rights, under EU legislation, have been contravened, the UK regulatory body is the Air Transport Users Council, Room K705, CAA House, 45-59 Kingsway, London, WC2B 6TE. (Phone 020 7240 6061)
http://www.caa.co.uk/default.aspx?catid=306
BA's Chief Executive can be contacted via the company's registered office:
William Walsh, MCILT,
Chief Executive,
British Airways plc,
Waterside,
P.O. Box 365,
Harmondsworth,
West Drayton,
UB7 0GB
Chris