My dose was:
15Gy (1x15Gy) HDR to prostate,
46Gy (23x2Gy) EBRT to prostate, and prophylactically to seminal vesicles and pelvic lymph nodes.
18-36 month HT (duration up to me in discussion with onco, but not decided yet - I don't have bad side effects).
This combo is called HDR Boost, pioneered by Mount Vernon with 2 hospitals in other countries, but it's now offered by all the main cancer centres which have HDR capability for high risk patients.
No SpaceOAR (was discussed and I could have had it on NHS, but not advised due to diagnosed high risk).
Only side effect ongoing is slight occasional rectal bleeding, no pain, no inconvenience. I was offered a 2 week referral to colorectal in the middle of the COVID-19 peak. Given I had a clean bowl screening colonoscopy a year before PCa treatment, and you don't get RT-induced bowl cancer 6 months after RT, and the bleeding is a common RT side effect, I said I was happy to wait until COVID-19 died down a bit - most unlikely to be bowl cancer.
HDR is different from LDR in that the treatment takes 10 mins, rather than 3-6 months. This changes the profile of the side effects. For HDR, they kick in pretty instantly, but also go very quickly. Urgency, urge incontinence, tiny bladder capacity (100ml when I came out of hospital, but had doubled in 2 days, and again in 2 weeks), and small continuous leak (I wore small incontinence pads). It was all resolved (and no more incontinence pads) after a month. My urine peak flow rate dropped from 25ml/sec before treatment to 10ml/sec. This didn't change for months and I assumed it would stay like that, but then it started increasing, and it's back to about 20ml/sec now.
Erections worked throughout whole procedure, but were painful just after the HDR because urethra didn't stretch long enough. This gradually fixed itself over next 3 months. I don't think this is a common side effect. Penile shortening is common, but is usually temporary, and mine recovered over those same 3 months. There is a risk of late onset shortening too, usually about 1cm if it happens. (Don't know how that compares with LDR.) There's also a risk of shortening due to HT if you don't regularly have erections or undertake penile rehabilitation, but this should be avoidable if you know you have to actively do something to avoid it (and most people are not told that).
I suspect the symptoms for LDR will last for some months, but might be less severe.
I'm a cyclist, and I cycled throughout the EBRT. I waited some days after the HDR, but was back on the bike very quickly. I did buy a noseless saddle so there's nothing under the prostate/perineum.
I extended my neoadjuvant hormone therapy (the part before radical treatment) out to 5 months, aiming to get my PSA down to 0.1 before RT (it was 0.12, which I was happy with). Since the treatment, it has been <0.01. At the moment, I've very happy with it, but I'm well aware many different things can still go wrong, ranging from late onset side effects (including ED) through to recurrence. I am a little surprised you are not being offered HT - it generally improves outcomes for the low dose rate RT treatments (EBRT and LDR brachy), but isn't of benefit for high dose rate treatments (HDR, Cyberknife and other highly hypofractionated RT).