From my own experience, I've found very good consistency wih the "industrial" tubes, 5693 is good, as is 6189, they are very close in operating characteristics to 12AU7 / ECC82. 12AU7 is actually more of an RF tube, though it is very common usage in audio. I found from testing a few 6189s in the Poseidon and ST70 drivers (with CCS long tail) that the 6189s showed better matching between the two triode sections, than did random 12AU7s. I have not tried 5693s in that application.
6CG7/6FQ7 are also very good, but they have the 6.3 V filament connections to pins 4 and 5, and 9 is either unused, or an internal shield. The 6CG7/6FQ7 is the 9 pin miniature version of the 6SN7, whichis an excellent audio tube. There are also 8 volt filament versions of the 6CG7/6FQ7 and 6SN7, I do not know if there is a European ECC-** equivalent for the 8V tubes
Tweak the circuit (resistance) values slightly, then you could use 12BH7A, 6GU7, 8GU7 and even 6350s, though the latter have a slightly different pinout.
/ed B in 73 degrees F (23C) sunny NC.