Next Wednesday

Hello
I've always understood the expression next Wednesday (or any other day) to mean the next Wednesday that comes along - so if today is Tuesday then "next Wednesday" is tomorrow.
But now I'm wondering if I've been labouring under a misapprehension. A friend told me that next Wednesday is actually shorthand for "Wednesday of next week" and that my usage is more correctly expressed by "this Wednesday" - which is shorthand for Wednesday of this week.

Is there a right and a wrong here? If not, then what is the most common usage - particularly in the UK.
Many Thanks
Jeff