Funny you ask this! I am going in for surgery on Monday- by the ENT specialist! The first appointment, as you've been told already, will take about 20 minutes or so depending on how much information is needed. If you have any questions, write them down so you don't forget to ask them -easily done in such a situation.
After the initial consultation, the consultant will arrange any tests you need and you'll be sent appointments or these. Sometimes, if an xray or blood test is needed, they might offer to do it the same day, but not essential if you don't feel up to it. Any scans etc will definitely be by appointment - might be several weeks, depending on the hospital waiting list. After the tests, you'll go back and see the specialist (or one of his team) for results and to be told what happens next.
You may be give medications at the time of your consultation and you may need to follow up with your GP if you need to continue them until your next appointment -but you'll be told what to do.
Hope this helps. pm me if I can help further. Janet