EDIT- This resolved itself in a relatively short amount of time.
I’m leaving this up so that people with the issue can see; as it is, the threads are unanswered and it gives the impression that this is still an issue!
I see that this is a relatively common issue! I have purchased premium, on the correct account. The transaction is complete and it shows as ‘active’ on my account page… but not ingame.
Attempted to tag AndyB as per the other threads but I’m unable, thanks in advance!