j_turner023:
I have finally had a response from VOSA:"I refer to your mail of 16 November to VOSA Technical following up a previous mail dated 5 November to VOSA and actually forwarded to this department on 9 November. I apololgise for the delay which is due to pressure of work.
VOSA did not allocate train weights to those drawbar vehicles which were produced prior to the introduction of goods vehicle type approval in 1982. In those days the only goods vehicles allocated train weights were articulated tractor units.
According to the above you can legally use this vehicle to draw your living van."
Tow what you like then as long as it is not deemed unsafe 
I saw a similar thread like this on a B category vehicle which was so old that no law covered what it could or could not tow
