That's... surprising. We've had some killer deals on Wii-U this past year (£199 deluxe models with various games thrown in like ZombiU/Mario/Luigi/LEGO etc.). Thought that might have at least pulled it up a bit, although I guess that means that VGC was overestimating their effect.
Nintendo really need to step things up over here. This summer TV seemed plastered with Luigi's Mansion 2 every ad break; haven't really seen anything similar for any Wii-U games.
I think they need to declare it a lost cause and focus on other territories instead of waste more resources. If there was hope, sure, but at 150K units, it's dead in the UK.