@mike-jones Yes, you’ll typically see this type of behaviour if there is another style that has higher priority in the sense that yours will be overridden. Using !important will override the higher preference, but should be used sparingly rather than everywhere.
@downpw I’m inclined to agree with this. There isn’t much else you can do, and provided it works with no odd looking artefacts in other browsers, then ok. The :before and :after are pseudo classes and very well supported across all browsers (except perhaps Internet Exploder, but who uses that these days ?)