I use a number of manufacturers for sourcing replacement tiles for floor restorations including Original Style tiles who are a manufacturer and distributor of traditional tiles based in Exeter, Devon since 1986. They offer a huge choice of high quality wall and floor tiles and mosaics in glass, stone, ceramic and porcelain, all suitable for residential locations, and most of them can be used in commercial settings too.
Original Style tiles can be purchased through a number of retailers around the UK, you will find more details on their website: www.originalstyle.com.