Getting paranoid - I need an external hard drive for weekly backups of my PC (approx. 8GB at present), which I can keep in a pocket of the laptop bag for a quick getaway in case the house catches fire or whatever. Looking at the products on offer, it seems to me I need a 2.5" drive, probably USB, and a capacity of around 500GB, at around £50. Does that sound reasonable, any recommendation as to brand and seller, and are there any hidden drawbacks I should be looking out for? How slowly do these things work? Many thanks in advance for all advice.