You may decide to which Hawaiian isle you will be flying to - either Honolulu, Maui Island or Lihue (Kauai island). You may even combine your flight with random of these airports (i.e. flying to Honolulu and departing from Luhue). British Airways promotional offer is valid for flights till 31st of March 2015. This offer is valid for bookings made till 3rd of February 2015 or until sold out. Paris and London are connected by many low-cost airlines such as EasyJet. One way tickets are currently available from just Ł31. To compare hotel rooms in Hawaii you may use this tool.
Important: Flights are operated by British Airways (and their partner American Airlines) with two stop-overs on your outbound way to Hawaii. There is longer layover in London however please remember that you can not skip the first leg CDG-LHR otherwise your flight would be cancelled without reimbursement.
Booking
samples
3. - 18.2.
17.2. - 2.3.
24.2. - 15.3.
9. - 30.3.
16.3. - 13.4.
Booking sample of an open-jaw flight from Europe to Hawaii for Ł433 here. In this case you would be flying from Paris to Honolulu on 16th of March and returning from USA back to London on 13th of April 2015.