I recommend traveling with Norse Atlantic
Flynorse.com

Departing from John F Kennedy (JFK)
Arriving London Gatwick (LGW)

Recommended flight options once in LGW

Easy Jet
Easyjet.com

British Airways
Britishairways.com

Departing from London Gatwick (LGW)
Arriving Santorini (JTR)

*** This is the cheapest route to Santorini***


Other Option

Depart from JFK - Athens
Athens - Santorini