I think that your tutor is simply trying to tell you what you'll find in the shops, rather than what you actually need.
Adobe does have some very different versions of Photoshop available. (e.g. Photoshop CS2 is far more flexible but vastly more complex than Photoshop Elements 5.0). However, Elements 5.0 isn't a different program to Elements 2, it's just the latest version of the same program. (i.e. if you go to PC World and ask for Photoshop Elements, you'll be offered only 5.0, because that's the current version). Version 2 was issued in 2002. Version 5 came out this year.
Elements 5.0 will have a few extra 'bells & whistles' to it but, basically, it's the same as version 2. (The chances are that you'll never really need the extra facilities anyway).
As I've said, the only version of Photoshop Elements which you'll find in places like PC World is version 5.0. However, you might find a supplier selling an older version (whether that be version 2 or an intermediate version) at a substantially lower price. If you're able to do so, I'd recommend opting for the older, cheaper version.
You should also check that the product you buy is compatible with your operating system. (Elements 5 will only run under Windows XP or 2000).
Amazon charge �59.97 for Elements 5. You can buy Elements 2, through Amazon, for �17.95.
Chris