The info related to your hiv fears are right on. I wanted to touch on the recommendation to seek help with mental health. I like that a clinic would make that when they think someone would benefit because that can indeed really help people lead a more peaceful life. If you gave an impression that you have an unhealthy relationship with alcohol (decisions during drinking that you'd never make otherwise, blacking out, major regret, etc.), this is often due to underlying reasons and often due to mental health. People self medicating if you will through booze. If you also were exhibiting a high level of anxiety, then this would maybe be something else they picked up on. Definitely if you tend to ruminate, overthink, what if scenarios plague you, then help with anxiety techniques in terms of coping would be great for you. So, not sure why they gave that recommendation but it could be something you would find beneficial.
The only risks for HIV in adults are:
1) Having unprotected (no condom) penetrative anal or vaginal sex, OR
2) Sharing IV drug equipment with other IV drug users.
You had no risk for HIV. There is no detail that you could add to this event that would make it a risk for HIV. Your GP and the sexual health clinic both gave you accurate information - you didn't need to test even once for this no-risk event, and you certainly don't need to test again. They probably just gave you a test because they thought it would ease your anxiety to see a negative result.