As the Daily Mail is not a newspaper of public record, I'll believe the following if/when officially announced. Might it pan out to be one Astute part time given the lack of permanent SSN facilities at Fleet Base West?
Reported by UK's Daily Mail on July 22, 2022:
"Britain is to send a fleet of nuclear submarines to the Pacific in a decisive move to thwart Chinese aggression in the region.
The dramatic decision could see UK subs based in Australia until 2040, operating within striking distance of China.
Admiral Sir Tony Radakin, the head of [UK] Armed Forces, will agree the arrangement at a naval conference in Sydney [week beginning July 25, 2022]. Assigning submarines to patrol the South China Sea will be Britain’s most assertive move yet against Beijing.
According to reports in Australia, Royal Navy submarines would be based at [Fleet Base West, Rockingham] on the country’s western coast and Australian submariners would be incorporated into British crews to improve their skills.
…The Royal Navy declined to say last night how many of its submarines could be relocated to Australia, as all operational details surrounding Britain’s sub-surface fleet are classified.
…Last night the MoD said: ‘It is UK policy that we do not comment on matters relating to submarine activity or operations.’…”