As advised on this forum, I had my first GUM clinic checkup at my 3 month punting mark (a while back). It was difficult to find and schedule an appointment at a free clinic, but I eventually managed to do so. The appointment slots are gone within minutes, so I had to call several days in a row at an exact time until I was lucky enough to get an appointment in the following days. This was ok for me, but could be quite bad if an appointment was needed for emergency symptoms, so I recommend sorting out your GUM clinic ahead of time in the event that you need one in an emergency situation. As for the appointment itself, I used a fake name and my punting contact (phone and email). I answered health questions and they gave me a urine test (from reading I knew to not urinate for 2+ hours prior to testing), and I also had my blood drawn for testing. A couple weeks later they texted with a message that everything was normal. (All clean after being with 50+ girls, albeit with reasonable safety precautions.) While at the GUM clinic I also asked about getting the Hepatitis vaccines as a preventive measure.
I was told that the Hepatitis A vaccine was only given to those at the highest risk; men who sleep with men, and that specifically rim each other. In other words, the high risk category for getting Hepatitis A was specifically rimming gay men (or transgender girls). But I think there is also a risk with rimming straight women, and maybe more so WGs. I have done this a couple of times so maybe I should get the Hep A vaccine? The other risk is food borne in certain countries like India or Thailand, but the clinic doesn't provide the vaccine for travel purposes. The vaccine itself requires two shots spaced out 6 months apart.
In contrast, punting was a general risk of Hepatitis B, so the Hep B vaccine was available. This requires three shots; shot#1, shot #2 after one month, and shot#3 after 6 months. For either risk category a blood test is done to determine if naturally immunity to the Hep A and/or Hep B viruses exists. My blood was drawn to test for Hep B immunity, and I was given the first Hep B vaccine immediately after. They said if I was immune I would not need the following shots.
So that was my first visit to a GUM clinic, which I thought I would share in case it might be useful to others.