wilf1980, I think you have given enough info for us get a feel for your history. If I understand, you had a scan and blood test, but have nothing definitive, beyond what they told you. You have recently moved and no longer have a GP doctor, or a Urologist? If so, then now is the time to be proactive and get both lined up. A GP for normal health issues and a Urologist to examine you closely for possible PCa or other prostate issues, because of your age and the confusing scan and blood results. Don't put any faith in those paid results, eihter positive or negative. Now is the time to settle in, get yourself a couple of docs who can help you determine your present stage of health, but especially get that Urologist, to get a baseline made for your health and so he can evaluate your future changes.
In answer to your question, cancer (PCa) is usually determined by either an elevated PSA reading during a normal PSA blood test screening, or a graduated increase of PSA blood tests over time, or by a abnormality found during a DRE (digital rectal exam). If any of these is suspicious, the usual next step is a transrectal biopsy of the prostate. From the point that any abnornality in any of tests (PSA OR DRE) are suspected, the medical testing and care should be referred to an Urologist for the remaining care. Consider a GP as a tripwire for detecting problems such as the first elevated PSA test result. In some cases, PSA will be elevated for BPE (benign prostate enlargement) or prostatitis (prostate infections), or even from sex a couple days before testing, or a DRE done before the blood draw, even.