I understand your grievances with the changes.
But unfortunately it's not "broken" or "badly designed", etc. - it's just a typical example of cunning retail strategy to rinse a few more pounds out of their customers before people cotton on to their new way of doing things.
It's been cleverly designed to catch out those who:
A) ASSUME that it will work the same today as it's always done.
B) ASSUME that if every other retailer works a particular way, Asda must surely work the same, too. (a very effective way to catch people out!)
C) Are too important busy to check the confirmation screen before committing to the purchase. (a good lesson here - today you've only done yourself out of 5 quid's worth of groceries. Next time it could be a vital clause in an insurance policy or mortgage/rental agreement, etc.)
Devious - Yes.
Immoral - Probably.
But perfectly above board and legal.
These big companies are only loyal to themselves - They don't care about us, despite what those cosy adverts might try to have us believe!
Confusing the customer is a standard retail tactic - tie them in knots, double-back a few times. Now they've got no idea whether they're getting a good deal or not!
I find that with the Domino's Pizza "Deals" - So many combinations, I can never figure out which is really the "best" deal for this order!