The closest thing to an OH-6A certified in Europe is probably this particular version of the Hughes 500, which I believe was certified as the H369HE and was refered to as the Hughes 369A.
Hughes 369HS, G-AYIA, Private
They were the first civilian versions delivered by Hughes in 1969. The instrument panel and rear doors were different from the OH-6A but otherwise they appear similar. The windows over the rear passenger compartment are of the larger variety commonly seen on the OH-6A. The later Hughes 500C has smaller overhead windows.
Hughes built a number of OH-6A demonstrators to promote the type in the late sixties and many were civil-registered and flown by the company at air shows around the world. They were never delivered to the U.S. Army. These, potentially, are the only OH-6As that might be eligible for inclusion on any civil register in Europe, except for the one mentioned by ppheli.
500 Fan.