Just as an update to this, had a look at some esata drives, but they were actually more expensive than the verbatim usb 3.0 2tb drive I was looking at, and the usb drive is plug and play - no mounting drives when plugging in.
Using windows backup (I'm soo cheap!) I backed up 180Gb data at around 50 Mb/s, and testing out a single 26Gb file on its own the transfer rate was up to 150 Mb/s. So I'm happy with that. The drive itself is suprisingly well built and dead easy to connect, doesn't look the most s****y bit of kit but seems to do the job.