Found this
Q "I have a Motor Caravan and a 1999 Transit Van - do I need to fit a Type Approved Towbar to them?"
A NO. Vans, Pick Ups (including double cabs, crew cabs), Chassis Cabs, Motor Homes, Personnaly imported vehicles (not bearing EC Type Approval), vehicles not for use on the public road and any vehicle classed as a motorcycle do not need a Type Approved towbar although in the case of the Transit Van most towbar manufactures would Type Approved there towbar for it.
http://www.towbarsdirect.co.uk/q_a.htm
This reads like you don't need type approval...