ok I went back and tried de-noise and de-hum. Neither did absolutely anything.
Well, I find this hugely-disappointing, Ant.
My only real experience was with that TC one, which I used a helluva lot back in the day. I even made CDs from cassettes recorded on portable (built-in condenser mics) home units where, back in the early '70s, my grandmother had taped relatives during rare family visits. I received crappy, grimy old cassettes from South Africa for the job. I was able to remove practically all spurious acoustic noise (suburban ambience), cassette hiss and also mechanical noises incurred from the belt-drive mechanism. Same story for AM radio when I taped numerous cricket broadcasts, and so on.
I didn't try guitar tracks 'cause I hadn't recorded any instruments since '94 (still haven't!), but I well remember feeling that I'd be all over this stuff by the time I eventually did some proper recording again. I was very excited, 'cause I envisioned not having to bother with gates ever again, such was the shockingly-impressive performance of the TC noise-finger-print-based system.
Oh well. I can only hope that there's something at least as good still out there, and not for the iZotope price! Seriously man, if there is, I'd love to hear what it can do for Cederick.