This is not available on the B&M website, hence posted as an INSTORE deal.
UPDATE: Possible price match with John Lewis - Many success stories! Not all - see latest posts!
The Karcher WV50 Window Vac is only £29.99 instore at B&M. I bought this yesterday from the Cardiff Bay store as I've been after one for a while and this is the cheapest that I've seen. There were at least 10+ left on the shelves and according to staff it is a nationwide deal. I thought this might be useful info for someone else.
The Kärcher Window Vac sucks surfaces dry and makes it easier to achieve streak free windows. It is also designed for removing liquid from other surfaces including mirrors, shower screens, tiles, condensation from windows and even spills from floors and worktops. The Kärcher Window Vac is a cordless, lightweight handheld product and with a rechargeable Lithium-ion battery, the Kärcher Window Vac can clean up to 45 windows on a single charge.