Point me to an Audible alternative that has remotely as good selection and pricing in the UK, and I'll have a look at it. I don't like the subscription model and wish there was an alternative.
A company like Amazon is not ethical. There's too many examples of disgusting practices from them to even count. Stop supporting them and find alternatives.
It won't be the cheapest, it won't have next-day delivery, it won't have as encompassing of a selection, but all of these come at huge human cost when you're talking about it on an Amazon scale.
[edit] Libraries offer a way to borrow audiobooks for free. Check https://www.overdrive.com/libraries to look for your local library's selection. Will definitely hit your pricing requirement and hopefully the selection requirement too!
Unfortunately I don't know how libraries work in the UK.