I encourage readers to support independent book shops. Most have an online ordering and delivery service and will order books for you. You can either have the book delivered, or collect it when you are in town, so there is no need to wait around for deliveries.
Localbookshops.co.uk is a directory of UK local bookshops, most with a physical bookshop on the high street, online
The Hive Network helps you buy books online while supporting local retailers at the same time. The website helps people locate local stores, collect books instore, and a percentage of all sales goes to local retailers.
The Booksellers Association has a searchable database of bookshops in the UK and Ireland. You can specifically search for independent bookshops and see maps of bookshop locations.
London Bookshop Map - this is a map of independent bookshops throughout the city, 106 and counting