It's a classic scam. There's not much British people love more than a bargain and these sort of 'panic sales' usually get people rushing through the doors (anyone remember the Woolworths closing down sale?). However, like with Woolworths, DVD/CD stock is very easy to resell back to trade so there's no point in HMV taking any kind of serious hit on the price, even if they are about to go into administration.
Higher speed broadband and larger hard drives means that HMV's death is inevitable. We're a pirate nation now . . .