This would be a "great" thread if only we had solutions for each other, except as commiseration is a kind of solution.
There is another thread similar to this one floating around, and I read every single post because I have this problem, too. I will say that that thread was somewhat diverted by contributors interested simply in narrow of wide shoes. Those we understand and they are not the problem or the solution. What we want is a shoe that has a more substantial "drop" in the heel to toe box ratio. The standard is a two size drop: a US D typically is a B heel and a D toe box. What we need is a A/D or B/E or C/EE. Etc.
I propose that a derby shoe may not provide the solution you hope, so be careful about ordering from the UK if doing so might entail a very pricy return shipment.
The problem with "our problem" with regard to derbies/bluchers are three
(1) There can be too much slack to tighten. If the facings close when you tighten them, you can't go any tighter
(2) You may end up tightening the top so much to prevent heel slippage that you cut off the circulation and get tingly feet (sounds fun, but it isn't)
(3) The facings become misaligned because there isn't enough foot in the heel and instep to hold the vamp in the correct position. You might get them to fit snug enough, but the eyelets appear to be completely out of whack.
I think Church's 103 last is the best for feet like ours, but if you consider why it is so you may be able to find other solutions. It is an extremely rounded toe with considerable "head-room" in the toe box but with a typically (for Church's) close fit overall. That is, the shoe really isn't all that wide, but the toe box is because it looks cool that way if you think it looks cool. Also the higher toe box "head room" allows the toes to move up and down more, which provides some comfort.
I have had decent luck with Allen Edmonds number 1 last, but only decent.
If anyone has had useful experiences, please share.