Hello Simon,
I'm very similar to you, age 48 with T3b staging early seminal vesicle invasion, 3+4 N0M0. The worry and and waiting for results has been the worst. I was advised by different professionals to go down both RP and HT/RT. The surgeons seems to favour RT and the oncologists surgery!
I've opted for HT/RT, I've just finished the 28 days of Bical, and am due my second injection of Zoladex at the end of the week. I'm pretty happy with my choice, but who knows if it will prove to be the best one, oh for a magic crystal ball to see the out come of both routes. The second surgeon I spoke to favoured HT/RT based quality of life, as he said with T3b, the surgery would be extensive with no nerve sparing, and also quite likely would require follow up RT. I'd initially thought surgery would be my route of choice, as I really didn't like the sound of HT side effects and was worried about increased risk of cancers later in life. Being young I felt I had enough time left for this to be a problem.
However speaking to the oncologist, there is obviously an increased chance, however it is small overall. I thought if I'm likely to need RT anyway, why have all the side effects of surgery as well.
I know its only been just over a month, but I've not really had any side effects from HT other than maybe feeling a bit more tired than usual, and some loss of libido but I've felt like that anyway since starting this journey just through the worry and lack of sleep! Anyway no hot flushes, sore nipples and boob growth. I've taken the advice of another member on here (Decho) to keep active so I'm cycling and doing some weights, to try and stave of muscle wastage as much as possible.
All the best with which route you take, everyone is different and unfortunately there no definite right answer it seems. I've been told I'll be on HT for a total of 2 years with 4 weeks of RT around mid October