I reckon
N11 bus from Stamford Brook (well, point where Chiswick High Rd becomes
King St) to Victoria. Every 30 mins throughout the night, timetable on
www.tfl.gov.uk.
Southern train from Victoria. These run all night. Timetables at
www.southernrailway.com or
www.nationalrail.co.uk
Hope this helps
Keith