Just been having a look at this. From what I can gather, there are 650 salons nationwide in the group that are hosting the offer and the nearest one to you, contacts you once you register your voucher. So, in effect you don't get a choice over which salon you go to, but with 650 to go at, there should be one fairly close to most people.
I'm definitely going to give it a try. Iwas thinking of getting ELC vouchers for dd's nursery when she leaves next month anyway, so now there's an added incentive