Hey there, good luck on your first ineterview. I did mine in NY back in April 2004.
In regards to your question, Silver gave some good advise. The main thing is that you want to look profesional, and I believe, you need to get a really nice siut to do that.
I went all out and bought a really nice Hugo Boss siut, very professional, but not too stiff. And it also really fit my age. I did wear slip shoes, but again, they were a really nice pair and looked really good with the siut. I wore a red tie with blue shirt for the interview, and also bought a less formal blue tie to wear at the coktail party.
I came from the regionals, so my income was very limited. But this is the type of interview which you want to look the part, and definetely don't want to look cheap.
As previously stated, make sure you are well groomed too (hair, fingernails, etc.). European companies pay real close attention to that. Nothing more embarrasing than shaking someones hand, and seeing that their fingernails are really long, or all dirty.