Hi Lexcat, I hope I can reassure you.
My daughter is 12 and started orthodontic work at 10. She had an undershot jaw (where her bottom teeth overlapped the top) and later on, crowding like you describe - undecended teeth showing on the x-ray but no gap at all to come down into. I was fully expecting her to have to have teeth removed and I was dreading it.
When she was 10 she had a removable plate to push outwards her top two teeth to get her bite the correct way round.
16 months ago (at 11) she had what is called a 'quad' - a permanent fixing across the roof of her mouth attached to her 4 molars to expand her jaw outwards to create more room.
12 months ago in addition she had the traditional tracks to straighten the newly descended teeth.
The quad came off a couple of months ago and in 6 weeks time the rest comes off. Her teeth are really straight now and I've been amazed at how fast and effective they've been.
Apart from a few minor issues adjusting to them at the start, her treatment has been unproblematic and painless, the most inconvenient thing has been the to-ing and fro-ing from school every six weeks to be honest!
I think it's amazing what they can do with teeth nowadays, DD's problems were quite severe but now, at almost 13, they look lovely.
Hope some of this helps you x