If interested in this promotional offer of Norwegian you may find the cheapest flights in November and December 2016 and January to March 2017. For a bit higher but still very attractive fare you may currenly book non-stop return flights from London to Caribbean Puerto Rico during the whole main season 2016/2017.
Booking samples
Oslo - Puerto Rico for €260 (NOK 2464)
Stockholm - Puerto Rico for €304 (SEK 2816)
Copenhagen - Puerto Rico for €317 (DKK 2367)
Travel dates are the easiest to check directly with Norwegian airline as they are offering full month view. To check your connection possibilities we recommend to use Skyscanner. This tool gives you quickly an idea which low-cost airlines are available from your home city. We recommend to book your hotel rooms in Caribbean in advance. To book your accommodation in Caribbean you may use Booking.com or consider following promo codes offered by Hotelopia or Venere.
Booking sample of cheap non-stop flights from Europe to Puerto Rico in Caribbean €260/£268 here. In this case you would be departing from London to San Juan on 10th of December. Your return flight from exotic Caribbean back to UK would take place on 21st of December 2016.