So my work blocks this site:
The Website you trying to access is categorized as Adult Material.
That's the default filters, and guess what it's blocking on ? Yup, matching subscription.php :S If you go to any other page it's fine, and if you switch on https it's fine too (inc sub page). So retarded.
The good news is, they are not doing DPI (deep packet inspection). Last time someone in the UK tried that (and before with Phorm) and they got majorly smacked by the EU Commision for breaching the ePrivacy Directive and Data Proection Directive. Fun bit is the EU highlighted how it was a breach of the UK's Regulation of Information Powers Act.