Hi Dean,
I had HDR Brachytherapy almost 2 years ago, at the time I had also been on HT for a year, so I didn't particularly notice tiredness, indeed I had no immediate side effects, and within weeks was able to down a few pints at the pub without getting my trousers wet.
However after about 6 months I got a prostate infection together with radiation cystitis, they are easily cured once you know what they are, but the symptoms are easy to miss. The first I knew about the prostate infection was getting a slight fever, I felt a bit like I was starting a cold or the flu, then I noticed a slight pain in my nether regions when sitting down. Once diagnosed it was easily cured with antibiotics, but I guess with winter coming on you are going to find it difficult to know whether you are starting a cold or a prostate infection.
The cystitis was noticeable by a stinging sensation when urinating, I found the cranberries the supermarkets sell this time of year, was the best remedy for that.
You will no doubt have follow up appointments with your consultant and his team, who will soon pick up and treat any side effects.
:)
Dave