DFT definition of a Dual Purpose vehicle..
"
Dual-purpose vehicle"
means a vehicle constructed or adapted for the carriage both of passengers and of goods or burden of any description, being a vehicle of which the unladen weight does not exceed 2,040 kilograms, and which satisfies the following conditions as to construction, namely:
a. the vehicle must be permanently fitted with a rigid roof, with or without a sliding panel;
b. the area to the rear of the driver's seat must -
i. be permanently fitted with at least one row of transverse seats (fixed or folding) for 2 or more passengers and those seats must be properly sprung or cushioned and provided with upholstered back-rests; attached either to the
seats or to a side or the floor of the vehicle; and
ii. be lit on each side and at the rear by a window or windows of glass or other transparent material having an area or aggregate area of not less than 1,850 square centimetres on each side and not less than 770, square centimetres at the rear; and
c. the distance between the rearmost part of the steering wheel and the back-rests of the row of transverse seats satisfying the requirements specified in sub-paragraph b(i) above or, if there is more than one such row of seats, the distance between the rearmost part of the steering wheel and the back-rests of the rearmost such row
must, when the seats are ready for use, be not less than one-third of the distance between the rear most part of the steering wheel and the rear most part of the floor of the vehicle.
Not much there that relates to a 110 van???