Thanks for your reply and the link worked fine. I really need a more complete solution than just the rotating base. The seat and seat support (box or struts) will need to be replaced as well given that the current one is a double seat.
I have a 2006 Trafic panel van I am converting. I looked at converting the passenger seat to a single swivelling seat. However you will have to be very careful that the seat will actually swivel. A friend had a factory fitted single seat which he converted but had to renew the fixings as nothing lined up. My main reaso for not going single swiveller was the loss of one passenger seat. You may have seen my gallery on here? If not it's under "Trafic Black Spot".