Details of attending the Winter Solstice at Stonehenge are now published- https://www.english-heritage.org.uk/visit/places/stonehenge/things-to-do/solstice/Winter-Solstice-2025/
Note that parking is very restricted, and must be pre-booked.
As is customary Salisbury Reds are running the special #333 bus up from central Salisbury- outbound from 0530 to 0640, back from 0915 to 1015- https://images-salisburyreds.passenger-website.com/downloads/Route%20333_Stonehenge%20Winter%20Solstice_web%20timetable_A4_1125%20v1_PRESS.pdf