An issue has been identified that's causing extreme slow connections to the hpHosts network, affecting;
Amongst others. I've ruled out the majority of the internal hardware, and suspect an external issue (will be speaking to the ISP once I've ruled out the rest of the hardware).
Apologies for the disruption folks, I hope to have it resolved asap.
Having went through the logs, checked the hardware and spoke to the ISP, I'm currently at a loss as to the cause of the problem. I'm going to get another router tomorrow (don't currently have a spare), to rule that out, and will be speaking to the ISP again if that doesn't resolve it.
At present, internal to external connections are working just fine, but external to internal isn't (internal to internal works just fine, albeit slower than normal, which is why I currently suspect the router).