The difference between the two is that HDR the radiation dose is put in and removed on the same day. With LDR radioactive pellets are left in. My main reason for asking is that I had HDR and I could relate my experiences, whereas if he had LDR I can only tell you what I have read.
If LDR the discharge letter may have said avoid pregnant women and young children for a month as there is a tiny amount of radiation still present for a few weeks.
For either of these there is the issue of the recovery from the relatively minor surgery. But for LDR there is the ongoing issue for a few weeks of ongoing radiation.
My personal experience is that HDR didn't make peeing in the night worse, but I have a pee bottle next to my bed, and it usually gets used once a night, sometimes not at all and occasionally twice a night.
If this continues to be a problem after a couple of months and it looks like it may be a permanent problem it is possible to use a disposable catheter just before bed time. If your local NHS provides a continence service they could help with this.