Could anyone advise me if I need to let my puppy's hair grow for a certain amount of time before I get a first groom for them? I didn't know if I was to do it at 4 months if it would affect their coat later on any advise please 
Yup, Dudley has got curlier with each cut and I trimmed the top of his tail as quite a lot of hair was sticking up, now he also has curls at the base and a dropped flag tail further down!My groomer is very keen to encourage owners to bring their young pups in so that the pup has an early positive experience, rather than the first time being to deal with a matted coat...
They won't cut your pup's coat, apart from a face and paw trim, if they need it and maybe a hygiene cut.
Others with more experience will tell you, but from Kiki, it seems to me once they have had their first cut, their coats tend to become curlier... Kiki had the base of her tail shavedand where it has grown in it is curly - the rest of her tail is a beautiful flag.