I'd wait to buy until you check your new PC's insides first unless you need to copy stuff over ASAP.

You can get cheap 3.5" external enclosures just about anywhere. Most newer ones support both SATA and IDE hard drives and the 5.25" ones will even support optical drives if you really want the expandability.

Just make sure it has atleast USB 2.0 and eSATA connections as eSATA is future proof (eSATA is the same SATA that you use inside the PC, only it has a cable/bracket that goes externally. So you get the benefit of using the SATA bus directly without the CPU hogging of USB 2.0). Some also have Firewire connections, also better than USB 2.0, but not widely supported.

Here's some UK stuff

_ _ - - = = Pr3tty F1y = = - - _ _