UK shared hosting customers are going to be subject to some downtime for their websites and email at 9pm tonight (UK time). A fault has been detected on a hard disk, which will need to be physically replaced.
Non-SSL websites will probably remain off-line until the new hard disk synchronises, which is expected to take around 2 hours.
Slowness can also be expected during the day of 18th September, whilst the server runs with less capacity due to the missing disk.
Update: All is now complete. The faulty hard drive was replaced and synchronised, and all is now back to normal.