I just thought that I would update you all with this.
After alot of time and significant financial cost (that doesnt really matter if I'm honest) Harley has been removed from all medication and appears to have made a really good recovery!!! He's put on alot of weight from the steroids and his working days are numbered but he is still a happy, excitable spaniel and should be able to live the rest of his years sat in front of the fire.