So I went on holiday to Greece nearly 2 years ago now. I went with a large group of friends and whilst out there one of my friends ended up making a tab with a bar. He didn't end up paying the tab, and as we were leaving Greece the bar owner had turned up, and the airport officials took us all into a room and took photocopies of our passports and said that we would need to pay the money when we got back to England.
I don't know if my friend has paid, we don't speak any more but it is worrying me so much as I am supposed to be going on holiday to Portugal this summer and I constantly keep thinking "what if i get arrested at the airport".
Is there any way of finding out if there is a European arrest warrant out in my name? If there is, what can I do to resolve this?

If I were you I would contact the authorities in Greece who detained you and arrange to pay the bar bill.

If Greece has an extradition treaty with Portugal (and I assume it does), you could be detained in Portugal pending a Greek extradition application.