I'm certain BALPA will have a view on the situation.
However, has anyone checked to see what the legal stance is when considering the following:
LIS based pilots are, presumably, on contracts that are water tight under Portuguese law and English EasyJet pilots are, presumably, on water tight UK contracts.
Would a UK based pilot be taking secondary action if asked to break a Portuguese contract based strike?
I'm certain that easyJet contracts will contain a stipulation that the company "reserves the right to make a pilot work at other network bases" (or such).
However, whether or not they can compel you to break a strike, in a foreign land, may be a point worth asking before accepting or declining such a Christmas morning offer.