http://www.elc.co.uk/Ball-Pit/122601,default,pd.html#pdpTab1
Hi this is the link to the Early Learning Centre website. You only buy the pit not the balls. The dimensions are 42in X 42in X 14in. It cost £9.00 from website and then postage on top of that. It is easy to assemble, and folds back down like a pop up tent, I haven't got it back like it came but can still fold it flat in a fashion so is easy to store.
Hope this helps