A car boot sale in north london refers to a specific event in the north London. A car boot specifically is similar to what we call a flea market. It specializes in secondhand goods. I also found an example of one where u could find bootlegs of all types. A good place to find more info is http://www.timeout.com/london/shopping/features/1786/Top_ten_car_boot_sales_around_London.html.
