Taking advantage of a working session at Didcot today, I checked out their 'Cone' (GW code name for GPV's) -

http://www.didcotrailwaycentre.org.uk/wagons/105781/105781.html

and took my own image -

She's obviously in a sorrier state now!

First thing to note - this is a 'Z4' - purpose-built for the job in 1939. It has square rather than rounded corners - but also has door-latches (missing in the kit)

so I then trotted off to the carriage shed where 'Iron Mink 11152 (http://www.didcotrailwaycentre.org.uk/wagons/11152/11152.html)

is undergoing restoration.

Note this is not a GPV variant (although the Z1's were based on this model) - BUT she also has door latches -

Ahah!! The car journey home was filled with thoughts on how to make four identical latches... After several near-misses I arrived home and ran a quick check on the kit. Definitely no door-latches. THEN I checked the image of 11136 in Russell' Wagons Apendix' and guess what? The full-page, works photo in stunning detail showed - NO DOOR LATCHES!

Moral of this entry - don't jump to conclusions and always check your sources! Comparing the kit to the Russell image - I can see where the design came from - and I don't have to worry about making those latches...