Toshiba external 3.5" HDD
As others have said, Toshiba have been selling such drives in the UK for several years now.
I bought my first two from PC World maybe three years ago when getting an external 250Gb drive for under £100 was cheaper than buying a 250Gb uncased drive from my local cheap parts supplier. Since then I've bought a few more on ebay, originally to get a spare power supply (as one had failed) but the "dead" drive I bought turned out to have a simple physical connector problem so I repaired that and bought another, repaired that too, and now have five that I rotate as my backup drives (when you can buy an external drive 500Gb for £30 it makes a fine backup drive)
One ebay purchase did arrive with a *dead* drive in it, but as has been said, dropping in another disk is simple. And the aluminium cases are excellent for head dissipation so very quiet in use (only the drive spinning and head clicking noises) ... and aside from that one power supply issue, I've never had a problem with either the case electronics or the drives within.
Early ones were PATA, more recent ones have been SATA. (And the PC World ones used a round four pin connector, while the ones from ebay have all used a standard barrel connector)
But they have all been USB2.0 *only* so this new drive may be the first with the eSATA connector.