Torque wrench recommendations

What about the beam-type ones? AFAIK Park have discontinued theirs, but I quite like the idea of having one that can't go out of calibration, and they should be cheaper. Are there any still available that cover typical bicycle torque ranges?

That type will still go out of calibration. You're compressing a spring and it will drift with time and use. You don't really need a calibrated torque wrench for bike parts, you just need to be in the ballpark of the correct torque so you don't strip things out.

I meant a big one for cassette lockrings/BBs etc.

Probably even less important for components done up as tight as these. It's unlikely to make any functional difference if a component asking for 50Nm is tightened to 40Nm or 60Nm. The threads are sufficient that they won't strip at the upper end.