Lacie external HDD's are very good. You sometimes pay a bit more for them, but the case designs are always clean and simple and fit into most environments, and the cases are well build. They normally use Seagate or Samsung drives too which is good.

As for internal drives. Try to go for Samsung or Seagate. Both good makes.

On Ebuyer.com they currently have a 1TB F1 Ecogreen SATAII HDD for £53.80 which is quite a bargain.

Or for more you can get a 1.5TB Seagate SATA drive, which is a faster 7200rpm one for £85.48.

1.5TB drives have just dropped to below £90 due to the new 2TB HDD's now available. However 2TB drives are not worth buying as they are currently overpriced at £160+. You could by 2x 1.5TB drives for the same and then have 3TB, or 3x 1TB for even less.