I don't think that they have the facilities for on line check in at CFN. As for seat selection on the CFN leg it is normally quiet so you will almost have the pick of any seat at check in, and if you don't get a seat you like, I am sure that if you have a word with the cabin crew, trim permitting, you will get to move. CFN is a long way from DUB and LHR, and I am not talking in terms of distance!