Just to clear a point up, already made, CORGI do not provide any accreditation whatsoever.
They are simply the registration body who administer the scheme.
The only Caravan Approved Workshop and Approved Mobile Workshop scheme is accredited by the NCC, the Caravan Club and the Camping and Caravanning Club, and is administered by Jones Vening.
It is NOT a prerequisite for service engineers to be CORGI registered to work on Privately owned caravan and motorcaravans.
It IS a requirement if they work on Static vans or caravans which are hired out as part of a business.
To become part of the Approved Workshop scheme however, engineers MUST have accreditation either by the old ACOPS scheme, or the new European Registration Scheme, which is under the auspices of the UK Accreditation Scheme as well as having passed the C&G in Caravan engineering exams.