"Priority List?"

At the beginning of August I was diagnosed with an accelerated cataract, caused by a head trauma ,and was told by my optician and doctor that because of the rapid change in my vision loss affecting my quality of life, preventing me driving and affecting work, I was classed as urgent. Despite a second referral I and speaking to the booking department I get told it will be about 18 weeks( Christmas) before I even get an appointment. When I asked if I could fill in for a cancellation I was told I cannot do this until I get an appointment. Is this correct? Is there no priority list orating?