AFAIK, TIP125s are still pretty common (at least in
America). I have
a bunch in my toolbox. Presumably there is a good European equivalent
that is easily sourced in the UK (much like there are easy European
equivalents to 2N3904/3906, etc). Just look for pretty generic power
Darlingtons and narrow your search down from there with the Hfe and Ic
parameters (and perhaps cutoff frequency).
FWIW, most ocmmon US (and Japanese) transistors are not hard to get here.
Certianly 2N3904s and 2N3906s are very common (I tend to buy they 50 at a
time..). I don't think you'll have any probkesm getting a TIP125 here
eiter. If you can't find oen, let me know and I'll see if I can find a
supplier.
-tony