You are of course technically correct, but the Consumer Contracts Regulations that are now in force give you the same, if not even greater protection. From a cursory glance at them, the time allowed seems to have been extended to 14 days.
The distance selling regulations may no longer be the act in force, but mentioning them certainly got me the desired result the week before Christmas when I was faced with an almost identical problem, the scratched and dented laptop I was sent, was replaced with one virtually indistinguishable from new, so it is worth the effort of standing up for your rights.