Thanks both! I did it and it was all fine - started to get a bit of a semi just as I was finishing but made a swift exit at that point! Already looking forward to going next week!
Glad that the habituation is already working for you. I think that's the key to it: using the showers regularly until the experience becomes banal and you stop thinking about your cock.
Personally, even though I'm gay and therefore am obviously attracted to male bodies, I've never had a serious problem with locker room boners - probably because I'm of a vintage where guys were expected to use communal facilities from a fairly young age and therefore had no choice but to get used to it quickly - but I think what happens with guys who do struggle with inappropriate erections is that they get stuck in a doom loop of anxiety. They think they're going to get hard, it starts happening, and then next time they're even more worried and it's more likely to happen again. The only way to break that cycle is to be brave, use the facilities anyway, but go in with coping mechanisms so you feel safer doing it - maybe if there's a shower head nearest the towel hooks that you can occupy, or thinking about some particularly dull problem you're trying to solve at work so as to take your mind off what's going on down there - and then wean yourself off them over time. Once the association between being exposed in the locker room and getting an erection starts to break down, then you'll find it progressively easier to go au naturel, until you no longer think about it and the problem is gone.
Of course, throughout our lives, but especially when we're younger, dicks can have a mind of their own and things may occasionally go wrong and you will get hard. I think what you do about that depends on the exact circumstances, but the thing to remember in that case is that erections are a common and ordinary part of a man's life and, so long as you don't go out of your way to be offensive in how you respond to yours (e.g. by wanking,) then it's really nobody else's business, even if you are embarrassed. I can only remember properly boning in an open shower once in my adult life: I would've been about 25, I was having a relaxing soak after a morning workout which felt really good to begin with, I *may* then have started thinking about what I had been up to the night before, and I was rock hard in seconds. It showed a disinterest in coming back down, and inevitably I was at the far end of the shower room, so I could do nothing but cover my manhood as best I could and simply walk out to get my towel.
The walk of shame was over in seconds and, although I think it likely one or two other men saw what I was doing, nobody said anything. No big deal.