2015 was the exception for Nine. Just 2 years earlier in 2013 they took the Sky UK feed. Although it looked great on GEM HD at the time.
This is how I recall previous Ashes series:
2019 - Sky UK via Nine (Exclusive)
2015 - Nine (Exclusive, no Fox Sports)
2013 - Sky UK via Nine / also on Fox Sports
2009 - Sky UK via SBS / also on Fox Sports
2005 - Channel 4 UK via SBS / Fox Sports?
2001 - Sky UK via Seven
Edit - Added @JohnsonTV’s info.
Edit 2 - Added @captaincupcake’s info