KitKatPacificUK has some valid points; I wouldn't choose to fly from Elstree as a qualified PPL. BUT that doesn't mean it should be out of bounds for a student:
1. Dodgy ATC- there is one AFISO who is notoriously bad tempered who does let the side down. The others tend to be fine.
2. The Runway - its not flat (it has a noticeable slope with a bit of a dip in the middle!), and its not in A1 condition, but its perfectly acceptable. The downslope means that solo (training?) circuits are banned on 08, this can a bit of a pain but it wasn't a huge problem for me.
3. Circuits - yes, they are completely bonkers, but not unmanageable. I did my tailwheel conversion at Turweston and found the circuit to be equally bizarre.
I'm not Elstree's biggest fan, and there certainly are better airfields you might want to take your custom - but its good enough so your nephew shouldn't be put off if it has to be Elstree.