Any membership will do but you should probably consider buying one or more EU roaming calls and texts addons as they give best value for money for making/receiving calls and texts.
http://community.48months.ie/t5/The-Newsroom/Cheaper-roaming-rates/m-p/3476/highlight/true#M19
If you don't buy the roaming calls/texts add-ons then you need cash credit on your account to cover the costs of making/receive calls and sending texts.
Your calls/texts while roaming will NOT be covered by your membership bundled calls/texts but you still need membership for the roaming calls/texts add-ons to work. If your membership will expire while abroad then maybe buy a new one in advance to avoid being offline.
Data roaming will not work abroad by the way so wifi is the only oprion for internet access.
See here for details of EU roaming charges with and without the EU roaming add-ons:
http://www.48months.ie/boiler-plate/other-call-charges
Hope this helps.
