There is something to be said for that, Paul and his people likely have an interest in the girls failing, as they can basically sold as slaves at that point, and all of those rich guys would probably like that. Not to mention using the images and videos we 'send' them for their catalogue.As far as who's providing Harriet with the goods it is hard to know yet. It COULD be Mykock himself, y'know, just to create chaos and getting more girls in trouble so they can get punished and therefore filmed... which would mean Harriet and Mykock know each other, which could mean Harriet might be our spy... It might also be Harriet herself stealing the goods when they arrive... or, the most likely (so far) in my opinion; Harriet and Maria Consuelo cut out some sort of deal where Maria gets her all the stuff you won't get in the school, like Charlotte's cigarrettes or Priti's chocolate and Harriet gives Maria, er... let's say some "relief" You know the question I haven't been able to figure out is; If Harriet can get you anything you want with her clandestine business, why didn't she get Liz some panties when they got stained... Some friend you are, Harriet!
As for your last question, I have to assume, because Liz was unwilling to pay for new ones. Either she did not have the money, or more likely, she just didn't want new ones.