ASDA have this Croc Rocker on sale for £12 if you click and collect or £14.95 if you need it delivered. If you wanted to take advantage of that delivery fee, look at the other summer toys*, like pools for £3 - £8 and so on.
I've been keeping an eye on a similar rocker to this, but from a different brand where it goes for over £30. I don't know how the quality compares, but this rocker is £12 reduced from £15 it should at least last a summer.
The reviews on it are pretty good - it has a 4.8 star rating (out of 5) for value for money. This review pretty much confirms what I think about it!
Had been looking at more expensive versions of this sort of rocker but prices always put me off buying. This is great for the price, fairly light but quite sturdy, I feel it will last a while even with my 1 and 4 year olds boisterous play.