LONDON — The prayer hall at the Liberal Jewish Cemetery in Willesden was packed on Wednesday afternoon with familiar fashion figures saying a final farewell to Joan Burstein, the retail trailblazer and founder of Browns in London. Guests at the memorial service — including Stephen Jones, Caroline Rush, Erdem Moralıoğlu, Nicole Farhi, Sam McKnight and Jonathan Newhouse — crammed onto benches in the chapel, while others, including Daphne Guinness and Yasmin Sewell, stood in the aisles. They remembered a woman who championed designers including John Galliano, Alexander McQueen and Hussein Chalayan when they were still students, and who, well into her 90s, still set a standard for style and strength. You May Also Like Rabbi Alexandra Wright of the Liberal Jewish Synagogue said Burstein was cremated in Ibiza, where she spent most of the year, and where she celebrated her 100th birthday in February.…