Missing details
11m WoW subscribers worldwide, you'd figure there's a fair few in the UK. At £10/month, if there's anywhere near a million subscribers, then that one game alone would be netting UK revenues comparable to PC game sales in UK stores. Then consider EVE and other MMORPGs, Steam and so on, and you have to conclude that the PC game figure is highly skewed.
Yes, PC game sales in stores may be dying out - because of late arrivals, variable playability and useless recommended specs, lack of ability to sell a game you've bought because of DRM, activation issues, etc. But that doesn't mean PC games are dying out - it just means they're being sold in different ways, whether it's to companies like PopCap with casual games, Steam for all kinds of games, or MMORPG subscriptions.