Hi, Fishy.
I'm sorry to see that you may have disease progression that requires further treatment, but welcome to the forum. At least your active surveillance has given you four years free of any possible side effects of radical treatments.
I was in a similar position to you. Initially diagnosed PSA 7, T2a, safely prostate confined, Gleason 6 (3+3). I went on AS. My three monthly PSA checks only fluctuated slightly. So I was surprised when a follow up MRI detected capsular breach and a subsequent biopsy showed significant change. Then T3a Gleason 8 (3+5), later upgraded to Gleason 9 (4+5).
Like you, I just got a phone call and a letter to see a consultant for ten minutes, to give me the bad news. I selected surgery. I had a much longer and in depth 30 minute consultation with my surgeon, about a month later.
I'm in North Lincs.
Good luck, mate. 👍