Hi Mike
I bought two tickets in K high 3/4 months ago and I felt similarly nervous about not receiving an email, so I emailed ACM and they responded straight away to confirm my tickets. Like you, I prefer something in writing when I shell out that kind of money!
I use Firefox as my browser and found that the ACM site simply wouldn’t work with Firefox – I spent a frustrating few hours and had to temporarily change to IE to buy the tickets.
Pauline