PM,
As a matter of interest, did you check the fare that was available to you directly by making the booking yourself on Easy's site, vs what a travel agent chose to charge you ? And how long before you traveled was this fare determined ?
Could you have booked a similar trip on Easyjet Holidays site at a lower total price ? Was there not an alternative tour-op offering on charters from NCL ? What was the difference in the EZY cost vs BA via LHR or LGW, or KLM via AMS, or AirFrance via CDG ?