Thank you Indinana and hildajenniJ for your advice. I have downloaded a knitted one from Ravelry ( BBbevan - its from a UK site, Black Sheep Wools) and the crochet one you passed on the link to. I am thrilled. Now I have to decide which one to do!
I've seen some lovely mermaid blankets on the internet, for children and adults. They look great for gc cuddling on the sofa. I think my gd would love one. Does anyone have a link or could recommend a pattern, knit or crochet? Sorry, if it is the wrong season for knitting but it might take me until Christmas to get it made!