Now that my small trailer has been sold off and the caravan chassis trailer has been cut up the lack of trailer gap has been filled with a FV2381 MKIII 750 kg cargo trailer aka 'Sankey Widetrack Trailer' although this one is made by Universal Engineering Company.
The MKIII widetrack trailers boast a drop down tailgate, hydraulic disc brakes, Repositioned handbrake (to allow land-rover door to be opened!) with consideration for the attachment of a brake-away cable, Heavy duty jockey wheel which has a swing away mount for stowing, and a tendency to rust between the wheel arch and tub.

Mine was fresh from MOD action tender and was in pretty good nick for a 10 year old trailer. Flaked paint and a slight bow in the rail of tub where the trailers where stacked piggy back style on the lorry, all the furniture was present and the mechanicals all working and showing sign of recent servicing (new brake hoses for instance).
I have since wired into the junction a standard 7 pin towing plug and cable (the MOD 12 pin is still present too), replaced all the 24volt bulb to 12volt equivalents.

12 Pin MOD Plug Pinout:

A and H: SPARE
B: Left hand stop
C: Convoy
D and L: Earth
E: tail and number plate light
F: Fog lamps
J: right hand stop light
K: Aux positive
M: Left hand indicator
N: right hand indicator

To cross wire to a standard plug:

Yellow 1 to M Left hand indicator
Blue 2 to F fog lights
White 3 to D Earth
Green 4 to N right hand indicator
Brown 5 to E tail and number plate light
Red 6 to B and J Left hand stop right hand stop light
Black 7 to E tail and number plate light

Painted inside the tub with etch primer and metal-cote black topcoat. Painted the outside of tub in NATO black. Waxoyled the entire underside and any other nooks that needed doing. Swapped the 650 tyres for 750's. Fitted a new breakaway cable.
Hopefully the trailer will last a good few years more without much attention.

Obtained a NATO tow hitch and fitted it to the dixon-bate adjustable drop plate. Not a bad example either as all the bits that supposed to move and rotate do so freely.

Does this mean a Sankey Trailer might be on the horizon?