Yep it's 3/4, and takes 1/2 inch hose. I couldn't find it in any local shops, and when you buy it online and add p&p it comes to more than I really want to pay for simply filling the pool...
But Carrefour isn't open on Sundays!
However you have just given me an idea...I am en France next weekend and could get it then (if it's cheap enough!!!
Or, seeing as JP has offered, I will borrow his!