Hello Bob, welcome here, sorry you have " joined the club". The radiation from Brachytherapy is not a danger to anyone else even children or pregnant women, prolonged contact for more than 10 minutes or so is not advised though, at least for the first few months.
If you wish you might put your Gleason score and stage etc in your profile, ir makes it a lot easier when offering advice.
Brachytherapy is usually for those of us who have a Gleason of 6 or 7 , PCa contained in the prostate, a prostate volume of around 50cc and so on. As usual in the medical world, these guidelines are treated as flexible, so vary from place to place.
I went to the Royal Berkshire in Reading for treatment ( not to far from you) and have had very good treatment. Side effects are, all joking put aside, really quite minor.
We all have to make our choices and since the outcomes are much the same I suppose it doesn't make much difference, my friend has had HT/RT and is reasonably happy with the results so far (apart from the side effects of the HT that is).
Good luck, keep us informed of how things are going.
John