The problem seems to have been resolved as of 16:20 on 16th April. I have not had a confirmation from our service provider but performance has been as normal for the last 10 minutes.
Access to some web sites has been slow since about 12:30 on 16th April 2014, those particularly likely to be noticed are at the BBC and some Facebook pages; the actual delay appears to be caused where these hosts bring in additional information from other servers.
The problem is due to a peering issue between Cogent, our service provider and TiNET who provide the services being adversely affected. The exact nature and cause of the problem are being investigated and whilst there is no guaranteed fix time Cogent expect full services to be restored by later this afternoon / early evening.
Sorry for any inconvenience caused.