Thank you both for your feedback, it's appreciated.
I'm after data integrity and ease of snapshots for backing up with minimum effect on a running system, so will be testing the following thoroughly before taking any action on my live servers:
1. ZFS on a 4GB Linode, using ditto blocks, without RAIDZ, for obvious reasons, as stated in my response to the accepted answer on serverfault.com:
http://bit.ly/1fXHimb. Linode have confirmed that the disk cloning mechanism will work with any filesystem; the only loss in features will be the inability to resize, or use the built-in backup add-on via Linode Manager.
2. SmartOS and Linux on Joyent's ZFS backed cloud. SmartOS looks very appealing from the perspective of the requirements outlined in this post, but their prices are considerably higher than Linode's. Joyent will be releasing the ability to install custom Linux images early next year, so that will also give me the ability to run Slackware with ZFS on what they claim is "bare metal" ZFS.
I hope to report back on my testing once complete.