Tyres.co.uk carries Michelin Agilis 3 and Pirelli Carrier All Season in the Volkswagen Transporter’s factory approved size 215/65 R16C. This size fits 6.1 Transporter models, too. Check your registration and door placard because wheel configurations differ, and you must meet the requirements for the associated commercial construction, load index, and speed rating.
To find the tyre sizes for the Volkswagen Transporters T6 and T6.1, look at the tyre pressure placard on the driver's side door of the front lock pillar. The placard shows the approved size and pressure for varying loads. You will have to use this placard and the tyre sidewall to check for the specifications for the registration.
The Volkswagen Transporter will not necessarily require four replacement tyres, but the handbook states that they all must be radial tyres of the same type. This same requirement applies to 4MOTION. If a matching pair can't be retained, then all four must be replaced. When replacing one axle, fit the new pair to the rear axle.