There are precious few places in Europe that have a direct connection to HE.net. They are only present in a few PoPs to begin with, and those that they are in are generally not the best choice for budget colo. The HE pop in NL, for example, is only allowable for colocating network equipment, not servers, so you have to pay a backhaul fee from another datacenter in order to get to the HE pop in NL.
I'm not 100% sure about germany, uk, or france, but it's probably a similar challenge.
You should definately convert the ATX boxes to rackmounts. Else you will pay a much higher price for power, as ATX towers are not very efficient to cool. You will also find, that renting racks instead of a private cage is much cheaper. Expect a large setup fee for a private cage.
interested in both. but we prefer direct contract with the carrier.
Your best bang for the dollar might be to find a provider that already has a cross connect to he.net that will let you ride that cross connect for a nominal fee. If you are really do a gig commit and can do it as a sub-commit, that might help them reach a higher level on their commit. Of course, that means they must have the spare capacity on their cross connect.