The laptop was feeling pretty slow with it's 5400rpm drive and the DVD drive hadn't worked for years anyway. With the buzz about Mountain Lion's Fusion drive technology reaching a peak I thought I'd give it a go.
The repair was simple - although I had a bit of trouble squeezing the Samsung 830 into the Optibay mount. Used the net guides to create a fusion drive and installed ML - all was good - until I noticed that the machine wouldn't sleep. Did a lot of trouble-shooting and ended up solving the issue by swapping the SSD to the existing HD slot and fitting the 500GB spinner to the Optibay mount. Feels like a new laptop now - definitely worth the upgrade.
1. Put the SSD into the existing 2.5" slot or the machine won't sleep.
2. Google "how to enable TRIM on Mac OS for non-apple SSDs"