@bear78-- My son went to both speech therapy and therapy for tongue thrust and both were immensely helpful. I highly recommend therapy. And if you go through your GP, it shouldn't be expensive. It wasn't in our case.
My son had speech issues as well due to the tongue thrust. So he went for the tongue thrust therapy first and then speech therapy. The tongue thrust therapy is not difficult but it does require patience and you have to stick to the program. We didn't see the doctor every week, but we were given a set of exercises to do for a certain period of time every single day. We had doctor visits every couple of weeks or so for her to check on his progress.
If you go through the whole program and follow the directions for the exercises, it works. Many people don't follow through and slack off with the exercises and then claim that the therapy doesn't work. The child has to put in an effort and the parent has to supervise. Of course it won't work if the child doesn't do the exercises.