Well I've still got my aligners in :-(
Turns out - on your last day of treatment, your dentist may decide to make you carry on for a few more weeks while whitening happens.
So on Wednesday I start my whitening with sort of a home kit, that takes FOUR WEEKS. For TWO of those I'll be wearing my aligners 22 hours a day, the other two I will start to just wear them at night.
I have to say I was a bit disappointed, but it's just to let the teeth settle into position for a little longer. Apparently it isn't unusual.