Hiring a Private Driver-Amalfi Coast

Has anyone heard of or used a Paolo Bellantonio at www.bellantoniolimoservice.com
How do you find out if they're reputable?
many thanks

You could check their web site for any testimonials perhaps. There's one here which has a few: Prestigerent

I would guess though that if you can afford to hire a chauffeur driven limo, then you're probably going to be staying at a five star hotel. In that particular case, they'll usually have their own tour desk that can arrange these things for you.