UPDATE:
I've been treating the yellow tang a day now with the Chloroquine phosphate, I didn't freshwater dip the fish as it wasn't looking really down with the whitespot (whatever the version it is-Ich, cryptocaryon, velvet etc.,) it was however, flicking quite regularly so needed quick treatment.
So the reason for the update was to relay that a day in and the tang no longer flicks, it isn't eating as much as before, certainly not the nori which it previously would wolf down, but at least the garlic infused brineshrimp are doing what they need to do-instill appetite.
This would indicate that the QP has either killed off the adult parasites, or minimum killed a lot of them to the point that it's not being bothered by them so much.
Firstly, I should point out that again, I'm going for the 10 day NO FILTRATION method as described before.
I'm guessing that the 10 days is to make sure all the trophonts are dead, and as the original method was 21 days with filtration, I don't see a problem with going slightly past the 10 day period.
I'm going to take the two 'boisterous' ocellaris back to the LFS to sell on to another customer.
Given that they came from a customer's tank, I do wonder if they had the same problem, and that's why they ended up in the LFS. A real shame as they're a good size and healthy and colourful too.
I will replace them with a pair of smaller perculas.