Hi Natalie,
My OH's work offers it, its a pre tax thing - so you get more for your money. I think there's a maximum amount per month you can sign up for or they can take a certain amount or a percentage - I'm not sure as we haven't looked into this yet (despite my nagging!).
So rather than pay for some of your childcare (it likely won't cover all of it) out of your after tax salary (from your bank account), some of it is paid in vouchers that are taken off your pay pre-tax, which means you get more for your money (and give less to the gvmt!).
That's how I understand it anyway. I am mad as my workplace won't offer it, if your workplace and your OH's workplace offers it, you can take advantage of it twice (it might mean you have to rework how you organise your joint finances) and get even more for your money. I also think (from friends who use the scheme) that you manage it and pay your childcare provider (topping it up where necessary with cash/chq) via the online system.
Hope that helps.
Valentine Xxx