It's a set fee, plus mileage, I think it varies depending on the size of the area. I'm wary of giving out specifics but based on the amount of work I expect it's considerably more than minimum wage (it's a fair bit north of £300 for a relatively small area with the correspondingly relatively small team).
There's two half-days you have to be in attendance - the training session and the day when you hand out paperwork to folk when they come to collect their books, then if I remember correctly there's an hour or two when you're available for people to hand their paperwork back to you and give you back any spare books a week later, otherwise it's just helping out with recruitment in your area for the couple of weeks prior to fill any gaps (though Deya do a lot of that themselves) and being available on the phone throughout the delivery week to chat to the deliverers in your area as and when they need it. I think I only texted my team leader two or three times when delivering last year. so I'm not anticipating more than half an hour per team member as a generous average. There's a possibility of follow-up stuff to be done if any of your team give you problems, but I'm hoping that won't happen! And of course, you can take a delivery route yourself for more money (and to save on your recruitment efforts, I guess ;D ). I may well be recruiting my husband!
I'll report back on the time spent/money given ratio after the event if it helps anyone for next year.
And also, once I get my area, I'll post the details on here if anyone wants to deliver for me (West Central Scotland) ;D