Have looks at i3D but also looking for other options - only needing a 1/4 so dealing directly with many of the DC's in Rotterdam is slightly difficult. Likely going to need to go through someone with cabinets within rather than direct.
SmartDC is the largest carrier neutral datacenter in Rotterdam, but does Secure half racks and up. They have Level3, global crossing, cogent inhouse, and many more such as nlix, eunetworks, eurofiber, colt, interoute, etcetera.
I3d is from 1u rackspace and up.
i3D.net (Deals) - Mail: firstname.lastname@example.org Specialized in on-demand infrastructure: Managed colocation & HP/Dell Intel Xeon E3, E5 servers Features: 36,000 sq ft datacenter, 10.000 servers, 370 Gb network, Amsterdam, Frankfurt, Washington DC, Los Angeles, Tokyo, Sydney Network Carriers: AMS-IX (Amsterdam), LINX (Juniper LAN), DE-CIX (Frankfurt), NL-ix PLIX, Any2 (California), Level3, Cogent, NTT, Deutsche Telekom (DTAG)