Well time for a quick update.
I've reinforced the join in the formers
After a great deal of head scratching and fiddling I'm confident that these pieces are all in the right place. I include a labelled picture to save anyone else building one of these a bit of time. The parts needed a little trimming, but not too much:
THe only bit that looks a bit odd is this one. If anyone has built one of these, does this go here? It's W25 and is shown on the fuselage assembly diagram. I doesn't seem to fit neatly. I may wait untill after I've built the wing, and I should be able to work it out then!