It's fabulous on a good day, and impossible on a foggy one (they get quite a lot of those).
All Class A airspace, so you need excellent VMC to fly there at all - 10nm vis if you don't have an IMC rating.
I'm not sure I'd be planning to fly round the Island. I'd land, hire a car, and drive around. Save your "fly-round" for departure.
And be VERY careful of the big new French TRAs and TPAs round the nuclear sites. They'll shoot you down or lock you up (or both) if you bust those.
Your friend needs to get the Bottlang plate (or equivalent) for the Channel Islands Zone and for Jersey, and to talk to ATC before flying there.
I found the clubs immensely friendly and helpful. Fuel is CHEAP, aircraft hire reasonable, but if you hire there, expect a thorough checkout (including procedures for flying in Class A).