PS Plus Essential - how to upgrade to Premium (12 months) with discount?

This is annoying. I recently downgraded my Essential PS account over xmas, as I wasn't getting any use out of the sub.

I pay £6.99 monthly.

I want to upgrade to Premium Annual with the 35% discount but there is no option to do this.

The ONLY option is to upgrade to Premium monthly and get 35% off this month's remaining pro rata upgrade price (£2.43).

Am I missing something or being dumb here, I cannot work out how to do this.

Thanks in advance for your help!