I'm in the unfortunate position where I'm waiting for appointments to come through from the referral unit.

Step 1:
Go to your local GP

Step 2:
Get referred to whichever test/consultant you're believed to need

Step 3:
Wait for referall team to send you a letter explaining how to book.

For the first of three tests, I called the number on the letter. This time (and because it was around 22:00 when I looked at the letter), I opted for the NHS provided choose and book system.

I logged in (good), but when I got to selecting appointments, there was no information on upcoming availability. When I tried to book one at random, I got the below.

Verdict:
Good to have a system in place, but should allow user research or at least return a relevant result which allows a Booker to book their appoint my.

Guess I'll call in the morning.