I did a little googling and found that it is common to run 82V lamps on 110V supplies. I don't know why it works (I can't get the numbers to work out, but my AC power theory is rusty). I do trust KHB though, so if that is what they say as well, then it sounds like it's right.
So yes, the setup you suggest sounds right: 240V mains -> step-down -> timer -> enlarger (82V lamp).
As with all these things, double check the power cable for any breaks or exposed wires - 110V is just as dangerous as 240V.