Call the Apple Store support number. 0800 048 0408.
You'll get an automated line.
When it asks what you want, say "I haven't received my order confirmation email".
It will ask you where you ordered and for your order number. Just follow the instructions.
It will confirm your email address (by spelling it out letter by letter).
Five mins later you'll have a confirmation email!
Worked for me. Couldn't believe it.
Wow.
Do I need to, though?