I have a flight booked from SYD>SIN>LHR and was planning on spending a evening in SIN seeing friends. They have been called away out of Singapore so will not be there. My flight is booked on miles from BMI, so the flight is no longer changeable with them, booked in J class.

Whats the likelihood of being able to change the flights at check-in in SYD to get an earlier connecting flight? Are SQ quite flexible with this?

Thanks.