We are aware of performance issues with our Xen VPS which has been introduced by security patches applied yesterday. You may see increased load averages and general sluggishness inside your VPS caused by CPU Steal.
We have a fix to resolve this, and will be rebooting each VPS node shortly to apply a fix. A further update will be posted here when complete.
Update: As of 19:00 UTC, this is completed and all VPS are operating normally.