You will need to remove 1 more seat to be legal wth a cat B licence after 1997. You do not need a pcv unless you are driving commercally or for hire and reward, just a test in a D! vehicle (minibus). But, if you are driving as a volunteer for a charity or non commercial body for a social purpose not for hire or reward, you can dive up to 17 seats,. You can only charge passengers for use of the vehicle if you have a minibus permit. I do not know if the social use for a non commercial body covers just family and friends.
By the way if you take the seat number below 10 it becomes a car and may require car tax to be payed. this used to be true but as a lot of van now have side windows the law may have changed.