Apologies if this has reached a wider audience already but put on to this by a friend*. As yet untested as the age-range does not suit any immediate research. Further info advised Births range 1837-1922 and Deaths range 1837-1887.
Pasted from GRO FAQ section: note Item 4 "Online View digital image".....
£2.50Standard Service
Your certificate(s) will be despatched on the fourth working day from receipt of your application (if a GRO index reference has been supplied), or the fifteenth working day (if a GRO index reference has not been supplied). We will send your certificate(s) to you using 2nd class postage.
PDF(s) will be available to view in your online account within four working days from the date of the order if we receive it before 4pm. You will be notified by email when the PDF is available.
Online View digital images will be available to view in your online account once the order has been completed.
Online Phone or Post
Full certificate with a GRO index reference supplied £11.00 £15.00
Full certificate without a GRO index reference supplied
(if customer requires the GRO to index on their behalf a fee of £3.00 is charged) £14.00 £18.00
Additional copy of the same certificate at the same time £11.00 £11.00
Online View digital image £2.50 n/a
PDF £7.00 n/a
Commemorative Certificate with a GRO index reference supplied £35.00 £39.00
Commemorative Certificate without a GRO index reference supplied £38.00 £42.00
Regret unable to fathom (*guidance was sketchy

) and haven't found the right link.