In terms of EU groups I have 80% in common with the "Group of the Progressive Alliance of Socialists and Social Democrats in the European Parliament" and 73% in common with the European Free Alliance. My support lies with the EFA however because there's a few other issues this poll didn't cover that are deal breakers for me.
By MEPs the standout one is Amelia Andersdotter of Sweden, a Pirate Party MEP. I have 83% in common with her. That said I also have 83% in common with Dolores Garcia-Hierro Caraballo of the Spanish Socialist Workers' Party. I have a lot of 80% ones, so many I cannot count.
By just partisan lines I have the most in common (80%) with various Socialist Workers Parties across Europe from Arbetarepartiet-Socialdemokraterne in Sweden to Parti Socialiste in Belgium, although Partidul Romania Mare is a wild card. I could go through them but there's a fair number, predominantly in "S&D" and the EFA. Plaid Cymru is my closest UK match and I rank consistently with their MEPs and such at 80%.
Interestingly with the SNP I only have 60% in common. That's because besides a few grey areas where the symbols indicate question marks and stuff I voted in favour of FTT and the extension of maternity leave. I think though I was a bit unsure about those grey areas myself so I think we have more in common than the percentage indicates. I suspect my closest match is actually with Sinn Fein, which is at 77% (my second highest percentage behind the ocean of 80s) because the question marks lie in all the right places.
But yes, on a UK level I have the following:
Plaid Cymru - 80%
Sinn Fein - 77%
Green Party - 73%
Labour Party - 67% (gasp!)
SNP - 60%
Lib Dems - 60%
Conservative Party - 27%
BNP - 27%
UKIP - 20%
DUP (Ulster) - 20%
UCU (Ulster) - 20%
My odd preference for Labour is down to Labour not having the SNP and Sinn Fein's weird gaps (one symbol was a guy with an exclamation mark above his head) although our main point of disagreement was over Bulgarians being allowed free access to the European job market, which they voted against. No surprise there.
You fellows should check your partisan political affiliations for the UK. I'd be interested to see, if you like I could tell you what parties in your own countries I seem to agree with most based on this poll.