If your lad is using it for Uni work and maybe a bit of media stuff (ie. watching films, playing music, etc.) then this should do the job:
<a class="postlink" href="http://www.johnlewis.com/acer-aspire-es1-512-laptop-intel-celeron-4gb-ram-500gb-15-6-black/p1747863" onclick="window.open(this.href);return false;">http://www.johnlewis.com/acer-aspire-es ... k/p1747863</a>
Acers are very decent these days (I have an Aspire, albeit a higher end one as I bought it to play games a few years back).
This has a 500GB hard drive which is more than enough space for what he'll need.
The only downside to this laptop is that it's Windows 8.1, which I think is a crap operating system but unavoidable these days.
John Lewis are a decent retailer, too (think they still offer long warranties but you should check).
Furthermore, with the £70 left in your budget you can pick up a Microsoft Office (doesn't need to be latest, can be an older version for less) so he'll have all the stuff he needs for his uni work. Or, download a software called LibreOffice, which is a free alternative and does the same thing.
Don't bother buying an anti virus - download a free one instead (I use Avast and Malwarebytes together; AVG is also decent)