I've been working on and off for Orridge for a year, a zero hour contract it certainly is, you can be the most reliable, fastest and accurate counter but it does not guarantee you any more work than someone that arrives late and is slow at counting. The planning of people on jobs doesn't make sense, there could be a job in your home town which you don't know about and your sent on a job miles and miles away. The hours are unsociable but sometimes its a help, a lot of people on jobs in London finishing late have to take night buses (like 2 hrs) just to get home but your not paid for that of course. I've not heard of anyone hitting the higher rates of pay for faster counting.
What I like about the jobs are that its varied everyday even if it does drive you mad in some shops and stockrooms. You get to meet a great variety of people and most supervisors are pretty decent.
The only thing you really learn is how bad some shops are being managed and kept clean!