I assume you are flying on a Sunday which has the later time, all other days still have a 14:!0 arrival so BA should be able to change your whole routing VCE-LHR-LAX either the day before or day after...or take the VCE-LHR the day before and have a night/day in London
I had a routing on BA flights where one had a schedule change where the connection no longer worked and was able to change both flights to a different date despite no redemption availability