Mat.
I have no first-hand knowledge of the quality of training currently provided by Naples air Centre, or the relationship between them and Bristol Groundschool. But a search within pprune archives for the period 2000 to about 2005 will reveal some interesting material.
If I remember correctly, Naples Air Centre was owned by a Captain Robert Gentile. He and Alex Whittingham engaged in some far-from-friendly debates at that time.
The fortunes of Naples air Centre then appeared to go into decline, with stories of unhappy customers.
It is of course possible that the situation is now completely different, and Naples Air Centre may indeed be a centre of excellence. But it does seem a little bit strange that they do not appear to have their own approvals, And Bristol Groundschool are not shouting out about their new outstation on their website.