Dog Training Job - Kenilworth, WC, 7708

I need a dog trainer who has a history of successful behavior modification in fearful puppies. My puppy is 8/9months old and has always been a fearful guy, but has been able to interact successfully with other dogs smaller than him. Bigger dogs resulted in a submissive fearful response from him and I actively try to not allow bigger dogs near him, either by blocking or us leaving. Recently his fear has turned into reactive behavior. Barking, lunging, at any dog he sees. I have been attempting to help him with counter conditioning training but I am hesitant to continue Incase I am not doing it correctly. I do not want to make him worse. So I am looking for someone who will be able to assist me with this training.