Rock bottom prices for 160GB drives:
Product Description: Seagate Barracuda 7200.9 - hard drive - 160 GB - SATA-300
Type: Hard drive - internal
Form Factor 3.5" x 1/4H
Weight 360 g
Interface Type Serial ATA-300
Data Transfer Rate 300 MBps
Average Seek Time 11 ms
Spindle Speed 7200 rpm
Buffer Size 2 MB
Manufacturer Warranty 5 years warranty
ebuyer have the list price as £31.39 and the package weight is under 500g hence it qualifies for the cheap shipping and google-checkout. Price is £23.97 after google-checkout with super-saver delivery selected.
Also Maxtor 160Gb, 2MB Cache, 3yr warranty:http://www.ebuyer.com/UK/product/120302
List price £29.97, add something cheap such as a mouse-mat (81818) to bring subtotal over £30 - with this mat and supersaver delivery total is £22.85 after google checkout.
UPDATE: Price for Seagate has gone up to £34.04 before discount, Maxtor still available for under £30 though