The unofficial car market is gaining mainstream approval, according to Cap, as getting finance and insurance becomes increasingly easy.
Robert Hester, editor of Grey Book, the trade guide to used grey import values, said: "This time last year buyers faced difficulties in securing finance for their import as many companies were not prepared to underwrite import business except on restrictive terms.
"This usually meant unrealistic advances and terms being imposed. It resulted in many dealers believing they had sold a car when in reality no finance meant no sale."
Now, he said, finance companies are more accepting. "Most will impose sensible advances and terms for grey imports."
"Buyers often had further problems in store when it came to insuring their car, because insurance companies would penalise grey imports," Mr Hester said.
"However, several companies now specialise in insuring them and even the likes of Tesco will provide cover - an indication of how far the grey import market has developed."