Hi Tom, I can't tell you what speeds you can expect but we have colo customers in our GS2 space, for whom we have delivered PSTN lines into their racks over which they use Dial-Up and/or DSL. They are very happy with them. It's perfectly feasible, we weren't charged any additional fee by BT either, regular PSTN install price as far as I know.
You should be able to get ADSL/2+ from the usual players via the Poplar exchange. Not sure about VDSL stuff though, maybe check Sam Knows or similar. If you drop me an email off list, we can provide you with Ethernet out-of-band connection there, or DSL, or possibly EFM or FTTC (if you drop my one of your existing PSTN numbers). We do IPv6 too. Cheers, James.
