Hi Fiona,
I had very similar symptoms to your husband.
I had HDR Brachytherapy in February 2015 and it wasn't until the August - September that the side effects kicked in, one was a dull background pain, that I noticed particularly immediately after I sat down on a hard seat, and I had frequent slight fevers like I was coming down with a cold. I also had the stinging urination pain of classic radiation cystitis which kicked in about the same time.
Urine tests at my GP showed that I was clear of urinary tract infections.
However at the next appointment with my Consultant, he immediately identified it as an infection of the prostate, which soon cleared up with some strong antibiotics he diagnosed from the hospital pharmacy. From the way he talked it seemed he almost expected me to have the post RT infection.
He started me on Tamsulosin which helped control the urge to urinate, however the cystitis took a little longer to clear, I ate lots of fresh cranberries over the Christmas which seem to do the trick (But beware the ready-made Cranberry Juice drinks sold in supermarkets, they are mostly sugar and water, you need the real thing 100% cranberries to sort the cystitis.
:)
Dave