This is the Wrenn W4318X Ventilated Van in BR Brown, running number B757051. Introduced by Wrenn, Basildon in Period 3, this continued in production until closure in 1992. As with all P3/4 Wagons it has metal rimmed wheels. These came with a standard grey roof (as shown in the picture) or darker grey roof depending upon the production run. Also you can just detect a slight  variation in the brown due to the plastic moulding mix at the time. 

Van comes complete with P3 box and yellow plastic insert,

Overall Condition "near mint" considering its age.