That's why it was doing that. I should pay more attention.
I run GWX @ 1920 x 1080 and have noticed the odd torp going off by itself, it just thought it needed some 'alone time'.
I think I can workaround it but as I really cba to find a more encompassing fix, I will probably just disable the Fire button and continue to use Ctrl+Enter.
Don't know how that sits with people.