Hi Chris, I just thought I'd reply to offer a tip. As well as having had PCa I also suffer chronic insomnia due to a sleep disorder. If you wake up at 3, if you're still awake at 3.15 - - - get up. This is the recommended 15 mins.
If you lie awake in bed suffering for any longer you get psychologically conditioned into associating being in bed with bad feelings. I've read that bed is for 2 things only S and S. Nothing else.
Our circadian rhythms are at their lowest about 2 - 3am particularly so if you're lying awake you can get some really dark thoughts.
Get up, have a pee and maybe a hot drink (no caffeine) and try again. Fifteen mins again.
If still no sleep have something to do planned that's distracting but not too stimulating. Avoid using anything that's backlit, e.g. TV or computer. Being exposed to too much light at night can disturb your circadian rhythm.
Hope this helps.