I'll be able to live-stream it now I've upgraded my broadband too
Turns out the reason my X carriage failed was because I was hanging a massive part cooling fan off the hotend mounting bosses, and they just aren't up to the job. They're aluminium nutsert-type things pressed in to a thin aluminium plate so really only strong enough to hold the hotend. All my fiddling and swapping parts etc has just stressed them beyond their service life - apparently its a known issue, but bizarrely I can not find a replacement carriage anywhere in the UK. There's only one site in the US which lists it, for a whole $5.
I have managed to bodge it back together with bits of PC case and cable ties for now so it will print again, and I've designed a new carriage which I will make from thicker aluminium plate. This will be much stronger, include a strain relief for the hotend wiring, and include mounting holes specifically for the larger part cooling fan so it doesn't hang off the hotend any more. I'm pondering getting the plate laser-cut for accuracy but I may just make it by hand in the workshop, depending on how long the bodge lasts
