I have read that page but when it comes to choosing a record it only offers "Certificates" at £15.
Very odd.
If you want a copy of a post-cut-off certificate, first find the entry you want in the birth, marriage or death index. If it's after the cut-off date, you'll get a listing with 'No image' against it, and then 'Order certificate'. Click on that and then on 'Add 1 to basket'.
Then click on 'Added to basket' and lo and behold, the charge is £12.