Gissing seems very good at portraying accents. For example, when Mrs Yule speaks I can instantly imagine how she sounds: with an old-fashioned, slightly gentrified, cockney accent. Her husband speaks in a rather blustering, educated accent. Harold Biffen enunciates very clearly. Jasper Millvain speaks very urbanely. Whelpdale has a very gentlemanly accent. Most of the characters would have spoken Received Pronunciation. The problem is, I wonder whether the accents I am attributing them are correct. There are not many tape recording from the 1880s. Most RP accents from film recordings of the mid-20th century are a bit different to how I imagine Biffen and Whelpdale and Alfred Yule speaking. Many of those accents, especially women's cut-glass accents, set my teeth on edge. When I do read a book by a British author from the mid-20th century, such as Lord of the Flies, A Town Like Alice, or even Watership Down, the characters do seem to speak with those mid-20th century RP accents. Incidentally, when modern British actors speak in historical costume dramas like Downton Abbey, they usually do not seem quite right to me. Their accents seem too modern. On the other hand, I wonder whether RP accents from the 1880s were actually like RP accents from the 1940s. They may have evolved quite a bit.
I may have to track down a recording of George Bernard Shaw. He was Irish, but he wrote Pygmalion, which was about teaching a working class girl a middle-class accent. He was also on the committee of the early days of the BBC when they decided to adopt RP as their preferred accent. He lived such a long time, that he may actually have had a late Victorian RP accent.
Interestingly, I found this article that referred to lost RP accents, which mentioned George Gissing, New Grub Street and Mrs Yule.