This, for me, is beyond risky - whilst DUB is a reasonably compact airport, there is a very high chance you'll have to clear both immigration and security, as that thread and the turnaround guide on the BA board indicates.

If you happen to be behind a non-EU arrival and there's a queue at immigration, or there's a group going through security (it's happened to me in Fast Track, and fortunately I had plenty of time) you're in trouble. The absolute best you could hope for is a 15 minute turnaround from exiting the plane - so that puts you back at the gate just five minutes before it closes.

Your C flights have enormous value - if I were you, and it's possible, I'd drop your original positioning flight and put the saving towards a new one and a hotel for the night. There's absolutely no way you're going to have peace-of-mind any other way, and I see no point in unnecessarily starting your journey stressed.