You can get a package like this for �160...
http://www.amazon.co.uk/Adobe-CS3-Web-Standard -Student/dp/B000OZ2EOQ/ref=sr_1_18?ie=UTF8&s=s oftware&qid=1201278398&sr=1-18
But I'm not sure your son will meet the educational requirements (it may be for uni use only -- but check).
It is the complete software though. You get the usual package, then have to email them with proof of your student status. Then you wait a few days for them to email you a serial number.
(I've used a similar offer to get CS3 design standard with photoshop, illustrator, etc.)
Finally, I'd question your purchasing of this in the first place. I assume he's doing some web design or something? Many designers (or rather, developers) don't use anything like this at all, and just write in raw HTML and CSS. This involves only free software that you can download yourself.
Plus, while he may be using the software now, he may change his mind (likely if he gets into it), and use other software.