Clue on Europe

Hi all, Plan to set up a 2 rack outpost in a colo in Europe. I am looking for prior experience(s) -- Good or ugly. My research leads me to believe that London and Amsterdam have the most dense connectivity. Is this true ? If so, then what colo's / ISPs in these 2 cities would you recommend. The primary aim is to get smallest RTTs to most of western Europe. - I would prefer a carrier neutral facility. - Backhaul to the US is a lesser concern but, of course, cheaper is better. - I have a small setup in the Isle of Dogs (London) presently, but the local loop charges are atrocious. - I am posting here instead of Euronog because I want to get US based prespective. Will summarize to list, Thanks !