Well, after 3 weeks the pool had turned a nasty green colour, had emptied of water a fair bit compared to when it was full, and the water on the rain cover (plastic dust sheet) was occupying more of the space in the pool than the water inside was!
Had to drain the pool and tomorrow will have to find something to clean the plastic with before it gets put away. I guess no-one’s going to be using it this year given that school starts again at the end of this week.