Pro: You save about £100k
Con: The CAA (for no sensible reason) will only issue a Permit to Fly, not a C of A. The Permit has restrictions, which I've heard include:
No passengers except crew. (This includes ground handling crew of course!)
Day VFR only. Not a big problem for most PPLs
No flights in Class D airspace
(Unconfirmed) problems getting insurance.
If you're seriously interested, I suggest you contact MW Helicopters at Stapleford airfield. Tel: 01708 88115.
MW Helicopters are the Gazelle experts. They've sold lots, and maintain about 40.
Speak to Martin Wood who'll be able to answer all your questions.