Q. Is the serial/Oxford comma generally used in British English? If the guidelines do not specify anything, what would be the appropriate usage?
A. You would think that the Oxford (or serial) comma would be popular in British English. And it is, but it’s not exactly British law.
The latest iteration of Oxford’s venerable style guide (New Hart’s Rules, 2nd ed., 2014; this guide, like Chicago’s, has its origins in the 1890s) supports its use but allows it to be omitted: “For a century it has been a part of Oxford University Press style to retain or impose this last comma consistently, to the extent that the convention has also come to be called the Oxford comma. . . . The general rule is that one style or the other should be used consistently. However, the last comma can serve to resolve ambiguity” (p. 77). Butcher’s Copy-Editing, published by Cambridge University Press (4th ed., 2006), likewise treats serial commas as optional: “A comma should be consistently omitted or included before the final ‘and’ or ‘or’ in lists of three or more items” (p. 156).
In its own text, the guide by Cambridge omits serial commas; Oxford’s retains them.
So for British English, use serial commas or omit them, but do so consistently. And if you go without, make sure to add a comma wherever its absence might create ambiguity.