I went to specifically buy some for my children and was willing to pay £15 each. I ended up finding them for £5 each.
The L/XL fits a tall 14 year old boy, it also fits me I'm size 10 and pregnant it comes up just above the knee.
Very soft and warm and makes it easier to get out of bed in the morning.
I bought mine from Westfield Primark in Shepherds Bush.
They had loads of colours and designs, I got my daughter a butterfly one. But mostly boys style design, games controllers etc.
Thought I would share as its a bargain and not advertised.