Or a Toshiba one for 50 quid on Amazon.
http://www.amazon.co.uk/gp/product/B00KWHJVCY?tag=hotukdeals03-21
(should probably note that by 2.5 inch what I really mean is usb bus powered. It's going to sit hidden in a shelf, I really don't care what size it is a long as it doesn't need a separate power cable)