if the apartment was your main home whilst in london then no you wouldn't pay capital gains tax for the time you lived in it. as far as i know, and you could check this on the inland revenue site or call them, but i seem to remember reading somewhere that you can let your main home for 3 years from when you move out and you dont pay CGT so long as you sell it within that 3 years which is what your case is.
also, as it was only a year, this year could be viewed as "actively marketing your home" - read into that what u want, without me getting told off !
really dont think you have anything to worry about. take your sterling, convert into euros and happy days and quids in (or euros as the case is). always make sure to keep your paperwork for the sale in case the irish authorities want to know where you got your money from. they dont seem to ask in ireland but the english banks do ask and actually log the amount in their records ! - but this is nothing to worry about if your affairs are above board (money laundering i guess)