Are you kidding me !!!
Here .. I will type reaaaaaallllll slow so you can try to keep up
The RETAILERS First option is to repair or replace
If a repair or replacement isn’t practical
A trader doesn’t have to offer you a replacement or repair if:
it’s too costly for the trader
it will take too long
it will cause you significant inconvenience, eg you’ll be without a phone for months
Or the RETAILERS other option is
If this happens, the trader should either:
offer you a partial refund if you return the item (to allow for the use you’ve had from it)
let you keep the item and give you a reduction in price for the fault”
So the RETAILER is the one making the decision, not constrained by any rights of the purchaser
No idea where your got the “inherent fault” from, certainly is not mentioned anywhere within the Act, once goods are accepted (and the use of the goods is in most instances deemed to be acceptance) then the right to reject (and subsequently the RIGHT to a refund) is lost.