? Yes you can. I use a Polish SIM card(with Play) and use it all year round in UK, except for the 2-3 weeks or so when I'm back in Poland for holidays.
[0] https://en.wikipedia.org/wiki/European_Union_roaming_regulat...
Calling you must be a bit of a pain. I just check and calling abroad from Lithuania is still 0.5 euro per minute...