We love this! Bought for a bargain from Kiddicare and currently on sale for under a tenner.
We love Kiddicare lots and their sale is great. One thing that really leaps out is this awesome water slide. We bought one two weeks ago (full price annoyingly!) and it is great.
Basically, it is 5m long and ideally you need a bit of a slope to make it work well as a slide. You should probably lob some Fairy Liquid on there too to make it properly slidey. Doofy loved it just being flat though.
Unroll it and blow it up. Next, attach a hosepipe to the standard fitting and switch on the tap. The water flows down the pipe and comes out of little sprinklers on the side of the slide, making it nice and wet and slippy.