So, I think I may have hit a bit of a luck.
Took a bit of a gamble on "a few old boxes of radio tubes" ad I recently spotted. Stuff arrived yesterday. 3 Boxes approximately 70cm x 50cm x 35cm, packed to the brim with mostly NOS tubes. 4th box contained a Stark 9-56 deluxe tube tester, complete with operator manual.
It took me about 5 hours to sift through the first box last night, and so far I've unearthed a bunch of tubes that I know have uses in guitar amps, as well as a boatload of others I need to do some further research on.
Off the top of my head, the ones I recognised were:
+- 15 GZ34's
4 or 5 5Y3's
a couple of EZ81's
10 6L6's and derivatives
a couple of KT66's
a couple of 6V6's
12 EL34's
about 8 or so EL37's
a bunch of EL84's
about 20 12AX7, AT7, AY7 type tubes
quite a few 6146's
Here's a pic of the first box as I opened it:
Shew whee! I think I have my work cut out for me sorting this lot out.