Generally, the free baggage allowance is 20kg for economy class; 30kg for the business class and 40kg for the first class. The excess luggage is usually charged at 1.5% of the full price of one single-trip ticket per kilogram. I know the Seven Seas Worldwide Ltd. which headquarters in Great Britain provides professional Excess Baggage Shipping Service; you can check their web for more info. Or, you can check your over-weighted luggage at the Shipping Department at the airport directly several hours before your flight time.