It is very difficult to be unambiguous with only the word next.
If, on a Friday or Saturday, I say "Next Wednesday", most Brits will assume I mean the very next Wednesday, less than 7 days away. If I say it on a Sunday or Monday, some Brits will assume I mean the Wednesday more than a week away. If I say "Wednesday next" on a Sunday or Monday, even more Brits (over a certain age, because "day-of-the-week next" is now a rather old fashioned expression) will assume I mean the Wednesday in the following week, thinking that "Wednesday next" is short for "Wednesday next week".
There are two potential sources of confusion here:
- Whether next means "the very next occurrence" or "the one next week" where "next week" means after the formal ending of the current week.
- Some vagueness over whether Sunday or Monday is the start of the week. (Honestly, some people see Saturday/Sunday as the bookends of the week, not the final two days).
Because of this, I tend to use "this coming Wednesday" or "Wednesday next week" to avoid confusion. Unless it's a Wednesday, Thursday, Friday or Saturday, of course