There is currently one 24 hour off licence in the London Borough of Harrow:
Sainsbury's, 12 Barters Walk, Pinner, Harrow, HA5 5LU - 020 8868 1399 (Not currently open 24 hours)
Please Note: Just because a shop is listed as having a 24 hour alcohol licence doesn't necessarily mean that the shop is open 24 hours a day, 7 days a week. It's also worth noting that large 24 hour supermarkets (Asda, Sainsbury's and Tesco) are not open all night on Saturday, Sunday and bank holidays (due to Sunday trading laws in England and Wales).