I have 1 of the Dapol ones that I gave a quick respray with a can of grey paint as a test. It was convincing enough, length issue aside that I went ahead and got 3 more KQAs, transfers and the brass kit from @Weshty to convert a rake of 4 of them. But I have made no progress as yet beyond that, as all of it is currently in a box in a storage unit for a house move.
The problem of course, is that for a large part of their life(when in service), they CPWs were loaded with 45ft containers which won't fit in the Dapol wagons for obvious reasons.