I'm having my surgery (covered by the NHS) on 2nd Dec. Here's the entire timeline from my first consultation to now.

18 July '17 - Initial referral from dentist to orthodontist at my local dental hospital.

8 Sept '17 - First consultation with orthodontist.

8 Jan '18 - First consultation with surgeon.

16 Feb '18 - Wisdom teeth and 2 molars are removed to make room for the brace.

11 May '18 - Braces go on. This would have happened about 2 months earlier but had to be rearranged twice.

8 Aug '19 - Orthodontist decides I am ready for surgery, arranges for appointment with my surgeon

20 Jan '20 - Meeting with surgeon. Ideally should have happened months sooner but there were delays in arranging an appointment. Surgeon agrees I am ready for surgery and I'm put on the waiting list.

1 Oct '20 - I am given 11th Nov as the date of my surgery. Appointments are arranged with my orthodontist and surgeon - these are eventually rearranged, along with the date of my surgery, due to my surgeon being off sick.

2 Nov '20 - Final appointments with my surgeon and orthodontist. Hooks are added to my brace for the elastics after surgery. My surgeon tells me how much my jaws will be moved by.

2 Dec '20 - Date of surgery.

Delays and long waiting times are usually to be expected with the NHS, unfortunately. If COVID hadn't happened I probably would have had my surgery around June/July. I'm in a similar boat to you, though. Not quite your age but I'm 25 now. I had a consultation with my surgeon and orthodontist back when I was 17 but wasn't sure if I really wanted it so put it off for about a year. Eventually decided I did want it and spoke to my dentist to see if she could refer me to the dental hospital. After about a year and a half of back and forth I finally got a letter from them offering me a consultation. Better late than never though!