Hello and Welcome Warchild
As far as I know the Xmas casuals do get paid weekly - but a week in hand. The ones in my mail centre do seem to have problems getting their correct payment and we usually see them weeks later in January/February coming in, trying to get it sorted out.
When you start seems to depend on where you work. In my mail centre the bulk of the Xmas Casuals start 3 weeks before Xmas and finish on Xmas Eve. A few might be taken on a week or so earlier. Some who are students start a week later when the Universities and Colleges break up.
If there is a lot of work they may be asked to stay on longer, sometimes until New Year, and occasionally into January.
But if there is not much work in the office they might get laid off - happened in my office a few years ago, and the casuals refused to leave the building. Management called the police to escort them out.
The Casuals are treated pretty badly by management in my office and sacked for being even a minute late.
Things might be different on deliveries.
But hope you enjoy it - just remember we have to do it year in, year out.
Good luck!
i got a quick question can somone tell us a bit about workin as a temp for royal mail as im gona be doing this ie is the pay weekly when dose the work start ie is it october ect any infomation would be great thanks and a big 
Cheers
Warchild.