You won't get far looking at other job ads. They'll mostly just say "competitive".
Look at sites like glassdoor.com and payscale.com.
Also try to find out if the company has a particular salary policy - e.g. national average + 5%. Lots don't (at least publically), but if they do, take it into account.
IT salaries can vary massively, according to employer (I get paid a lot more on the private sector than I did doing exactly the same thing in the public sector, and it's still a lot less than I could get if I worked in banking.) It also depends on skill set - some skills are worth more than others. Security is quite hot at the moment; they already know what his work is like and he's now got a first. Obviously he hasn't got masses of experience yet, but I should think he could push for quite a bit more than £30k. Also, consider things like number of days leave, other benefits (private health, gym, pension,) and flexibility. Though if it's for an internship, not permanent, not all will be available.
He needs to know what the lowest limit is that he'd accept, but don't tell them. He also needs to know what he expects, having done research and he should probably start with asking for a bit more, then there's room for negotiation. He's in a strong position - make the most of it.
I hate salary negotiation, too. It's pretty normal in IT, but most techy staff never get taught how to negotiate - plus it perpetuates salary gaps.