HDD's are only going up for the next 4-6 months by all accounts.
all good UK component stores, often having short offers, i've never really seen anything around christmas especially though. Amazon themselves may not have the volume, the independents that use amazon as a front won't have the volume and have to pay amazon as well. The above stores are often cheaper.
Actually I've just checked and am surprised at amazons prices, not to bad really, shop around though. Lots of bundle offers on scan for instance.