(Click the Union Jack on the lower left corner for the English version of this site)
The second seller for arcade parts in Europe I found so far (besides www.arcadeshop.de). This one is from France, however their site is in English as well. The program is various, they don't have everything, but do have some interesting things that are pretty hard to get here, like real arcade monitors, Sanwa parts and even a Seimitshu Spinner !
I haven't dealt with Starcab yet, but from what I hear is they ship quickly. Prices are pretty good as well.
Thanks to Darth Nuno of http://www.dragonslairfans.com who pointed me to Starcab.