You can find a very detailed description of how Jews integrated into English society here. The only bit directly about the Sabbath is this:
Another feature of the Jewish religion which tended to set its adherents apart was Sabbath observance. Two aspects of this were evident to the general public. First, that Jews did not trade on Saturday. H. Miles Brown, writing in 1961 of Emanuel Cohen in Redruth, notes that 'local tradition says he was a practising Jew, and could be seen waiting for sunset on Friday and Saturday evening to close and open the shop'.23 It must have made a very powerful impression for the tradition to be extant over a century later. The second aspect which was widely noticed was the law which forbade a Jew to light a fire on the Sabbath day. A Jewish family would often employ a Gentile to tend its fires and put on, or turn off, lights. So common was this practice that there was a popular term for such a person - a Jews' Poker.24
However, keep in mind that most Jews at the time were working as small shopkeepers and tradesmen. (See the same reference.) As such, they could essentially make their own hours. Whether the Tobacconist is open on Saturday is up to the owner, so an owner who keeps it open M-F can still be said to be integrating with his gentile customers.
The other part of the answer is simply that many may simply have not observed the Sabbath. I can't find numbers for this, but if you look at the 1851 religious census in England
Pressure for further change was encouraged when the 1851 census revealed that out of a population of nearly 18 million, only 5.2 million attended Church of England services, with 4.9 million attending other Christian places of worship.
So at the time, only around half of Christians attended church. If you had similar behavior among Jews, you'd expect a large number not observing the Sabbath. (Which is of course what you see today in modern society)