So if he was at SOAS, presumably it was arts/hum/socsci, OP? If so, funding options are far thinner on the ground than in sciences, and he's going to be looking at best at the research council rate - so 15-7k ish tax free stipend. He needs to get a funded place - he's incredibly unlikely to get a permanent job without this, as it's about the only evidence of ability to obtain significant funding an early career person can get. (Essential criteria on most jd 's nowadays, even in the MN- despised post 92s)
Preferably also that should be research council funding as opposed to institutional, but full funding is key. In the general area, London universities have lots of potential for postdoc or tf posts, but you're almost certainly going to have to move or he may have a long commute at some stage before he gets a job that's permanent - possibly even to Europe/the Gulf (lots of money for junior posts in these areas)
No harm in looking to see what's out there - jobs.ac.uk have PhD's advertised all year round, as people get major grants with studentships attached etc However, he's likely to be up against similarly qualified applicants throughout: unusual these days to get full funding without a distinction at MA+first in undergrad outside of science. Not unknown - former student of mine has done it on a 67 at MA with a distinction for the dissertation, in SW DTC area- but not common. Internal applicants can have an advantage if they're considered to be good also, so worth him checking out SOAS first to see what they say.
Like much nowadays, though, it's not enough to be excellent: you also have to be lucky.