I have just received an email from our host pre-warning me about some downtime this weekend.

Dear Chris,
This weekend we are happy to announce that we are moving all our servers to a new datacenter. This will bring a great improvement to the service we offer, as, along with extra network connectivity, the new datacenter is fully redundant by N+1 for UPS, Generator and HVAC.
Unfortunately, when a physical move is being undertaken, there will be a period of downtime - however we hope to keep this to a minimum. The task will be started at around 9am GMT on Saturday and we hope to have everything moved over in 2 hours. There will then be a further (hopefully) brief downtime period whilst all the DNS records update, but we hope this to be an hour at max.
Please bare this in mind.

Thank you.