if lawyer wants contingency then he will make more money on it and you will get less money. Amount of work in this case, I think, is limited. Going to celebrity lawyer maybe a mistake. And paying for work maybe a better outcome since after first case most other cases are about the same.
as long as you claim refund right before Jan 15, you will have time after that to find the right lawyer, but should be done ASAP
Then, rather than committing the mistake of paying this guy a huge amount of refunds by going to mass action...
Why don't you start a collective fund so that this guy takes one person and works on the case to it's conclusion. If he succeeds then you can get cheaper lawyers to do the light work of referring to the first case as a precedent (assuming that even applied).
This would make it easier on the pocketbook of customers and leave the lawyer with a less than fat wallet.