IMO the UK radio landscape is in a far better position than in Australia for one main reason. They have a strong BBC that has popular stations with big listening audiences. R1, R2 and R4 in particular. As commercial radio goes into decline they’ll still have the BBC stations that are mainstream and popular. Australia doesn’t have this with the ABC. Instead the ABC has tiny audiences and niche programs, and is largely stuck on AM in the capitals. It’s really quite dire.
Also, I’d point out that national programming works a bit better in a small county like the UK compared to the vastness of Australia. You can drive from London to Edinburgh in 7 hours, it’s just not the same. The Brits are also far more used to fully national programming on popular stations like R1 and R2, and even the likes of Virgin Radio in the early days.
Outside of Sydney and Melbourne there’s a very limited choice of formats on commercial FM. Look at Brisbane, 3x CHR stations and 1 bogan sport/greatest hits station. Regional areas are just horrendous for the most part. I think Australian radio will die long before the UK.