I saw these wagons in a book many years ago and thought that it would be another conversion for the ever faithful Hornby TTA. I purchased the tank ends from, I think, Mendip Models in the mid eighties and the conversion started. The thing that attracted me to these tanks was that they had their ladders on the barrel and not the ends, this was quite different to other builds.
I decided on a rake of three, and I run these either on their own or part of a BP Company train with Class A tanks.
Again hardly a difficult conversion, but something a bit different.