Update @2020-05-07:

After having effectively mothballed the project for a year or so some early Es activity has prompted me to get building again. The boom and passive elements were all completed last year, left to do is the driven element and feed, and the boom mounting method.

I've mostly build the driven element and matching section - and it's tuned out quite neat too (metalwork we never a strength of mine). I'm particularly pleased that the 2 75Ω bits of coax fit in the feed box - this makes the whole setup much more tidy although I don't know what this will do to the RF properties, so it may need to change. This arrangement was only possible by using RG179 for the matching coax, which limits the power handling to 200W (and possibly less due to the coaxes proximity to other metalwork). This is fine for now but will need to change if I decide to run more power in the future. If this does happen it should be fairly trivial to rebuild the feed box without having to drastically alter the rest of the antenna.