Sadly the frame-straightening attempt did not go well – partly because the frame was more bent that I thought - the seat tube is really quite far off being straight, which was presumably why the frame-builder I saw said it would need the tubes heating. I can't justify spending at least £225 on the work needed (including a new paint job). It feels crap having to scrap what was decent frame, but there you go. At least it wasn't anything rare or unusual.
Speaking of which, the replacement is fairly rare, coming from a small frame builder who was only really working for about a decade, from what I can tell. There's not much info on the net, but I did find this:
"Atom Cycles was the trading name of artisan frame builder Andrew Thomson who worked out of his own premises in Hazel Grove near Manchester in the 1990s. Andrew learned his skills from Frank Herety the renowned Stockport frame builder."
Which makes sense as I picked this up in Stockport. It has a fair amount of scrapes and also rust in places, but isn't looking too bad so I'll keep it as it is apart from some touch-ups, for now at least. At some point it'll probably need a respray but that can wait.
Clearly I was fated to get this, as not only had it been knocking around on FB for ages with no interest (I actually nearly bought it instead of the Holdsworth), oddly someone has at some point added a very crap attempt at a Holdsworth head badge:
Obviously that's coming off, first thing. Luckily they kept the other decals on, as the only frame number I can find is a very faint '16 1', so there's no way I could have identified this otherwise. The second job is that there is a stubborn bottom bracket cup to remove, where I'll try the thread and washers technique to hold the removal tool on whilst using a large spanner.
Anyway, good and bad news, I suppose...