Canary, I appreciate it may well be different in the UK, so please feel free to ignore my advice.
For what it's worth, I have worked for doctors and the consultant leaving you hanging may not really have a grasp of what you're going through. I would, politely but firmly, contact their office/nurse/receptionist/whomever and explain the situation, concisely but clearly. Then ask the best way to get a message to the consultant: email, voicemail, written letter, message with the nurse/office staff, telegram, what have you. Then I would contact the consultant once in that way, with all the information. I would wait a short time after you know they have the communication, maybe 2-3 business days, and then keep contacting them at intervals until you get the information you need.
If you get someone on the phone who is sympathetic, get their name and talk to that person each time. If you can get an email address, I would go that route, as it leaves a paper trail. Failing that, you might write a letter, and fax it and mail it.
If the admiral nurse or your GP or similar can advocate for you, that's another possible route.
If I have overstepped, please forgive me. I know physicians are overworked, but cannot abide a doctor or doctor's office, who will not help a patient.