Cataract Surgery

Hi I recently was advised after a eye test that that I had cataracts in both eyes and required cataract surgery. I have company medical insurance through the company I work for and diced to contact the insurance company. I was informed that the insurance covered Cataract surgery and I would have to pay £100 excess, which I taught was great news and arranged for the surgery through the BMI saxon clinic, I was informed by the surgeon that the operations would be carried out at Stoke Mandeville hospital, I initially had the left eye don and was handed a big bag of eye medication Dexafree, Chloramphenicol and Acular . ta week later I had the right eye don and received another large bag of Dexafree, Chloramphenicol and Acular. The results of the cataract surgery was absolutely brilliant opened up a whole new world for me, the colors were so vivid and I didn't need my glass anymore. The surgeon and treatment was during and after the operation was brilliant. The surgeon instructed me to carry on taking using the medication / eye drops for six weeks, I did mention that the medication I received would last a lot longer than six weeks and could I return whats left to the hospital, I was informed the hospital would not taken any medication issued back, I did that seems a bit of a waste what would I do with the reemergence, she said you will have to bin the reemergence. About six weeks late I received a letter from the insurers acknowledging that they had payed in full the invoice for the operations, however they did not cover the medication which costs £176 and I would have to pay Stoke Mandiville directly, I did say that when I contacted the insurers I was informed that they would cover the whole operations and I consider the medication as after care, and informed them the name of the person I spoke to, they said they would check phone call recored and get back to me, still not hear anything.
I have just received an invoice direct from Stoke Mandeville simply stating £176 for taken home prescription drugs 20. Although I don't mind paying for the medication if the insurance does not cover it, however I am not happy with paying for the excess medication that was given to me. Has anyone got any advice on how I should proceed.