In reply to Nim:
Grandfather (estate joiner and all-rounder for all his working life, whole life in same very rural(*) area near the N. Yorkshire / County Durham border) pronounced them to rhyme with "out"
* rural but not the sticks, only 8 miles from a major town
I've never heard "owt" pronounced "oat" in my life
I guess I've heard "nowt" pronounced "note" but I used to assume it was just Harrogate/Ripon people with pretensions to being posh, an assumption that was, in my mind, concreted when I heard Southerners doing the same (presumably as an inversion, i.e. trying to sound LESS posh and more "gnarly")