You seem to be stuck with us '70s leftovers, for some strange reason!
Here is an alphabetical list, off the top of my head, of names that could be found on downtubes about 1975-79. British builders who were building at that time, or the shops that badged their frames... Any one of them would have built you a nice frame. In combination with a 531db decal, (or Columbus or Super Vitus or Ishiwata) many of them would not build with anything less, - I would have been glad to ride any of them. Apologies to anyone I've overlooked... I don't doubt Midlife can fill in the gaps...
You can do a search on anything in this post and know as much as I do within a week. Do an image search and see some beautiful bikes... If you need '80s, someone else will have to help!