Piers12, may I join your thread as someone on a rather parallel journey?
I had surgery in 2016, and PSA was under 0.05 (the detection limit for the hospital lab) for 2 years then very slowly started rising. Even when it reached the threshold of 0.2 there were a couple more 3-monthly tests to check it was still rising before referral to an oncologist.
It is interesting that different hospitals (or maybe different doctors) make slightly different decisions about the best treatment. Both the surgeon and oncologist thought a scan was unlikely to be informative at the current PSA level (0.31 a month ago, prior to the oncology appointment). But also that the prospects were much better to have radiotherapy sooner rather than later - apparently PSA under 0.5 with doubling time of over 6 months gives the best chance of success. They clearly judge that for me the recurrence is likely to be located in the prostate bed; probably because there was about 2 mm of positive margin according to the path report post-surgery.
There seems to be some discussion with these statistics about whether to have hormone therapy alongside radiotherapy, and I accepted the advice of the oncologist - who after all is the expert on radiotherapy - to have it. I started on bicalutimide next day, with a Zoladex injection 2 weeks later and stopping bicalutimide 2 weeks after that (this week). Apparently being on bicalutimide reduces the risk of immediate side effects when starting Zoladex. Radiotherapy is planned after 3 months of Zoladex, with it continued for 3 months after.
So it is a bit of a trip into the unknown, and I have done a lot less agonising than you but simply jumped in quickly when advised. So far no drastic side effects from the hormones, though I do want more sleep and EF is clearly affected (it was already tadalafil-dependent). The nurse giving me the Zoladex injection said I should expect a growing waistline though.
Your PSA is increasing a bit faster than mine, so you will need to make a decision soon I suspect. Good luck!