It was my favourite book when i was a kid of around 7 and i am 42 now. So we are talking around 1976-78. Apparently my Dad got so sick of it as i didn't want any other book than 'Sally'! I have goggled it but not found it anywhere. I just wandered if other people out there remember it at all?
If you look on Abebooks there is a book called 'Sally's birthday party and Trouble in the toyshop' by Yvonne Perrin, published in 1970. It is reasonably priced under £5, but there is only one copy listed. If it is the right book, you might want to snap it up quickly!