This was originally published in Australia in 1976, before books took on a more violent tone. The first 'scene' takes place in a library, where a 12-year-old boy meets a girl his age who happens to like one of his favorite authors (Rosemary Sutcliff). When Laurie returns home, he finds that his parents have bought an antique brass bed for him. When conditions are right (I'm avoiding spoilers) he awakens in the same bed, but in London, 1862. So along with time travel, there's a vivid description of life in London during the mid 1800s. It's a fun read, nicely paced, with a 'tidy' ending.
July 2016: I was browsing an unsorted box of postcards, all priced at a quarter. One of the cards, dated 1906, was of a 'crossing sweeper' in London. I hadn't heard that term until I read this book. Too bad the message didn't refer to the image on the card.