Fair point, gbs! I wasn't being glib.
I would have recommended Bike Shed in Exeter, which I have had good dealings with in the past, but they are too far away from your son. I mentioned bike shops in Plymouth to them before and they suggested Bike Cellar was a good shop and had a reliable workshop. This was a few years ago, but I can't imagine things would have changed: it's still owned and run by the same people.
Or, if your son is that way inclined, he could try and have a go at servicing the bike himself, or am I correct in assuming he's at uni there, and hasn't got the time to do
that kind of thing!
There are planty of maintenance manuals to guide you or, even better, there are excellent videos on youtube for all manners of repairs and maintenance.