Hey nrwigley!
I'm not from the UK, but from mainland Europe so I do know the trouble of looking for B&B necks over here when ALL THE GOOD STUFF is somewhere far away (Musikraft) and therefore costy... so nothing out of UK (except guitarbuild) - but from China (they ship everywhere) and Germany.
But you're lucky that you aren't looking for a Jaguar neck! :-P
From what I've sourced and searched throughout the last years... and luckily I've found one that works for me:
I found this one on Ebay-kleinanzeigen (Germany) for a little more than 300€ - it's said to be Japanese... but I had zero information about the seller... so these exist. It also needed those F-style Tuners - or at least I have such installed.
Alternatively you could source a Fender Made in China Coronado neck (also big Headstock, but a rounder curve.
https://www.ebay.com/itm/353791331046?h ... SwzmthptyE
I also got one of those for an upcoming project - so - just that you know - the seller is cool to work with - he has some necks to choose from and it's always pics of the actual neck - so if you want more grain in the fretboard or the back of the neck... just watch the pics closely.
(might be of interest to some: he also has a 2018 Squier Deluxe Jazzmaster neck for sale - so still Rosewood - and it's the J Mascis profile if I'm not mixing something up here)
If you insist on not having the truss rod access on the neck,
there is Hermann's guitar in Germany - but selling worldwide
https://www.ebay.de/itm/304006941242?ha ... Sw2ghgqiqr
Those are most likely Chinese necks* so it might be hit or miss - but from what I've heard he has a higher quality control than some others and raving reviews! I had two B&B necks that looked damn similar from an Austrian seller - also about half the price but this might have been the issue - and while modern tuners might have fitted, Kluson tuners did not because the space(s) between the tuner holes was inconsistent some bigger some smaller... so just make sure (to ask) whether these would fit or not.
*Another reason why I believe that: Hermann's guitars also sell some guitar bodies - and hi-etimesmall (the Coronado neck seller) sells the same or very similar parts for much less.
Alternatively:
Wait for the new Japan Jazzblaster or an 60th Anniversary Jazzmaster (not big headstock though) gets parted out - on Stratosphere or Reverb. Or look for JM66 or Vintage parts.
Or: let guitarbuild.co.uk build you one.
Does anyone of you have any info on how good they are/how they look? Because a custom made neck for 205 pounds doesn't turn me off at the slightest (with custom headstock shape - you have to send it to them) any info on the Block size would be cool too! BUT: There is no (online) option to make it a bound neck...
https://www.guitarbuild.co.uk/collectio ... uitar-neck
I hope this helps at least a little.