Lesson here is:
If you want a guarantee to get a copy on launch. Get it yourself, there are loads everywhere.
If you want to risk it, buy it online and put the game in the hands of Royal Mail/Yodel...
If you don't mind not having it on launch and want to get the best price, get it online.
It applied for almost everything these days, it is rare they sold out as they know this game will sell so they have printed millions of copies in advance. No way they want to lose out of potential profit by not getting your money.