May I be honest, not negative, just honest here?
You have a couple of problems.
First, anonymity could be a problem. Those committing to go will want to know who else is on the list, and I cannot imgaine anyone being prepared to pay anything until they know who else is going. Plus I can't see anyone dropping out once they've paid as that means losing money, so you need to be transparent with all of this.
Secondly, who's going to share rooms? And who will decide who's going to share with who? You may have mixed sex travellers, and thats only going to cause serious upset somewhere. I know I wouldn't consider sharing with a total stranger. The alternative is single supplements, which will prove costly, if you find an operator prepared to let you have a number of rooms for singles when they could fill them with 2 or more people. Hotels and chalets are geared up for 2 people sharing, and holidays are costed accordingly. Apartments obviously can be for more sharing, but then you've got the same issue of putting people together. Plus you'll only get group discounts if you fill accommodation space.
Finally, have you considered where everyone lives? Some will be in remote parts of the UK, in Scotland, Ireland maybe, or even further afield. You'll find that Tigner holiday packages involve flights, and the standard is Gatwick which could be an issue for some people, impossible for others. Regional flights, IF available, attract a premium.
Like I said, just trying to offer some honest views here and raise the kind of concerns that I have covered when planning holidays in the past.
Personally, I think you now need to go public with those who are expressing a serious interest in going on this trip. Now you've decided on
Tignes, which I assume was the majority, you might find people not wanting to go there and pulling out perhaps? I think it would be a good idea for those going to know who else is on the list, so they can decide to pull out should they discover their arch J2ski Nemesis might also be going, and also cover off where they would fly from. Knowing what gender they are will also be helpful as well as relevant.
Not trying to steal anyone's thunder here as I have no intention of organising this kind of thing myself, but trying to make suggestions that would help.