Presumably the ones you have that came as standard with the van are the continental type sockets made by a company called Berker..It is possible to buy the same sort ( with no switch )but have the 3pin British type socket..have a look hereYour dealer should have them or get one for you. We couldnt get the same ones on our last van but the dealer got 2 for me. Its an easy job to do for a competent diy-er
Kevin