I want to buy my 18 week old some clothes from Frugi but he's sort of between sizes on their size guide. His waist is too big for the 3-6 but the length is way too long on the 6-12. Does anyone know how the size compares to Next/M&S so I've got some sort of idea? Everything 3-6 from Next is too tight on his waist now but M&S 3-6 is still fitting him. I want stuff that will fit him now for over the summer not really that he has to grow into 