New box - when to expect visits?

I think you're going through a similar process to me in terms of initially worrying if the kit you've got is acceptable to the birds.
Based on my experiences last year I'd urge you not to worry - birds have very different eyes to us that respond very differently to light levels. Yes it's true that the presence of a lamp where it would normally be dark is probably not 'ideal' for them, but when it comes down to choosing where to nest I think it's far more about how sturdy and sheltered they perceive the box to be, and most crucially whether they're able to access the right food at the right time in the vicinity.

Of course I could be wrong!

But don't worry about the lamp is all I'm saying

Also the way my box/can setup went was: a bit of interest initially from BTs in the first year, followed by a GT rooster over that winter, followed early last yr by a bit of battling between roosting GT and very interested BTs, ending up with GT just disappearing and BTs carrying on with the full nest/eggs/chicks/fledging.

So you might not have much actual nesting luck in year 1....or who knows, never say never!