Given the score was 12-0 at the time of the "try" surely the final score would have been 12-7 (given the conversion was made) as the penalty would not have been given so no 3 pts, the penalty in the second half would not have been given either as the circumstances that led to it would no have occurred.
Yes, correct. I'd thought it was brought back for a scrum which England collapsed giving Wales the penalty but it wasn't. The try was disallowed but Wales got a penalty instead so wouldn't have had both scores.
Not that I've moaned about the try disallowed, though, that was someone else. Once a decision is made, it's made.