If you telephone DAF they will give plenty of advice, they are a lovely team. I use Real Pet Grub at hillsborough, but that may be too far out for you, check them out on facebook.
DAF do deliver to individuals but in mot sure on the quantities, we dont have a chest freezer (or the space for one) so we shop weekly at RPG.
The DAF stuff is pre packaged into 1lb bags, and if you work in rough half or even quarters you wont go too far wrong, its easy to serve that way rather than weighing precisely.
If you have the chance though, pop down to Real Pet Grub, speak to the lovely family down their, and they will give you as much or as little help as you need.
Good luck with the change