Excel will lease Finnair 757, not sure what reg this year, in addition to a Sunwing Airlines 738. The Flyjet 757 also operates flights on behalf of XL. Excel do tend to use alot of aircraft, not from their own fleet for flights during the summer. EMA, BHX and BRS all have aircraft from foreign carriers operating, maybe it is more financially viable to do this than having a fleet of aircraft which operates fully in summer, but not so much work to do in winter.
Interesting piece of news on BBC Look North about expansion of airport etc.