There are also rebates available...
There is a printer rebate available on almost all the printers, allowing you to get a free printer/scanner combo after rebate.
There is also a iPod touch rebate, when your a student you get a free iPod touch when you buy a Mac.
Also save getting the expensive Office suite which isn't really like the Office your used to on windows, instead get iWork which is cheaper and better designed, its also compatible with Office files and integrates better with the OS as well as following the same interface design as the rest of the computer unlike Office. Its reduced in price when you buy a Mac.
Mobile me is also often reduced in price when you buy it with a computer so ask if thats the case.
Finally with Snow Leopard the latest verision of Mac OS X just around the corner you can get a free upgrade obviously just paying the £7.95 fee for taxes and shipping.
A few deals you might consider when you go in which can help. Finally AppleCare is about £48 when a student down from about £200 normally and is well worth it as any repair on your computer will cost more than that and computers can and do regularly fail so its peace of mind and it has saved me probably about £3,000 on the products I have ever had, assuming that I would have been paying for them. Plus there is telephone support too!
Let us know what you get!