Hi, Rashid.
Welcome to the forum, mate.
I'm not medically qualified and do not feel informed enough to comment on the different treatment paths suggested by Belfast and London.
I suspect, your PSA levels since surgery may be helpful, how many have you had and what were they. Do you have your pre surgery PSA level, cancer staging and Gleason score and your post-op histology, including any extraprostatic extension or positive margins.
As far as I'm aware, biochemical recurrence is usually defined as being PSA at 0.2. Yours is considerably lower and at these low levels scans have often have difficulty in detecting any remaining rogue cells.
We have posters who've gone though salvage radiotherapy may be they'll be able to help with your query.
Best of luck. 👍