Know UK legislation.
The 'money laundering' legislation in the United Kingdom, under Sections 327 to 340 of the Proceeds of Crime Act 2002 (PoCA), is wide-ranging and encompasses mere possession of criminal or terrorist property as well as its acquisition, transfer, removal, use, conversion, concealment or disguise. In the UK 'money laundering' need not involve money (it relates to assets of any kind, both tangible and intangible, and to the avoidance of a liability) and need not involve laundering either (a thief's possession of the assets he himself stole is included). There is no lower limit to what has to be reported - a suspicious transaction involving a single £5 note may be required to be reported.
Thanks for the heads up Sash, this may come in handy.