The NHS has really good speech and language therapists. There are also lots of talking tips. Search “talking tips” and “ECAT” on you tube.
You can get your doctor to refer your child, or the school to refer your child to the NHS speech and language therapists. If either aren’t helpful you can actually approach your boroughs Primary School advisory team through the council.
if you need a private one Mummy then ring Rozzy the owner of Marmalade Cat, Marmalade Bear etc - She has lots of nursery schools and will know which of the speech and language therapists are actually working at the moment. Good luck with it.