Not relevant for this build, but for others interested in the conversion, I asked Z-Cars about their plans for the sump and the ECU as they're the two most important bits for me; the engine is too tall for a normal mini and especially for my Minus and the ECU Charlie used was £1500 and three times the cost of the rest of the engine! Z-Cars are working on a slimmer sump to get the engine under the normal round-nose body and, more interestingly, they are using the standard Ford ECU, though I've no idea how they plan to make it work.
Will be interesting to see how the Z-Cars conversion looks when it's ready.