Ford Mondeo MK2 V Reg - A/C Refrigerant leak?

Are there any good tips or tricks to find out where the refrigerant gas is escaping from..... such as air test the system and use soapy water??

I cant afford to be replacing loads of parts in the hope that it works so need to target exactly where the gas is leaking from. Its a gradual leak over a couple of months or so.

Many thanks for your help and advice in advance!

Matthew
April 2009