Up until this week the only place I could find annatto seeds and achiote powder in London was Cool Chile. Then I was wandering around New Loon Moon in Chinatown looking for some staples and stumbled across them in the back room. 50p for a 10g packet of achiote powder or 55p for a packet of annatto seeds (can’t remember the weight of this bag).

New Loon Moon
9a Gerrard Street