London is great - I’ve visited many times. If you live in London, you may be able to get a Freedom pass - free travel on tube, buses and discounted taxis. Arrive at any tube station, and you can ask for help without any notice. They’ll guide you to and from your train and help you find a seat. If you need to change trains or aren’t sure how to exit at your destination, they’ll radio ahead and someone will meet you and guide you through the station. You’ll hear them refer to you as a VIP, which I enjoy - but it stands for visually impaired person. All London buses announce each stop in advance, which is super helpful. The bus stops are listed in Google maps and identifiable with names and letters, which is great when there are several stops together.

If you live outside of London, you may be able to apply for a free bus pass that works anywhere in the UK (including London) and purchase a disabled railcard with gives 30% off for yourself and a companion. You can also book assistance on national trains by using the Passenger Assist app or phone line.

The UK is pretty great for events too. Many venues will seat you close to the stage and provide a free ticket for a companion. Some of theatres also offer touch tours, live audio description and a guide dog crèche.

It could also be worth reaching out to the guide dogs charity. They have a sighted volunteer scheme, which could be useful if you want someone to help you try out different routes to your local store etc. They also offer things like additional cane training.

One thing, we don’t use blocks here. For example in America someone might say it’s three blocks down, I don’t know what that means.

The dating scene is hard, at least for me, I can’t really say much about it because I don’t really date.

Some traffic lights beep. Otherwise go to the box at the right of the crossing and there should be a tactile indication that spins when it is safe to cross

I’m not in either city so can’t give much other detail - though I recall Nottingham being fine. I get lost if I try to use the tube alone but London buses are comprehensive

I'm Irish but I've been told Dublin and London are similar enough. I've also lived in the UK for about a year.
Public transportation is good, but it will take getting used to! Make sure to get in touch with your local RNIB resource workers through your school.
Audible traffic lights are hit and miss. In my experience they either beep, or there's a small spinning cone at the bottom. You place your hand on the cone(cylinder???) And once it rotates faster it's safe to cross.
Tactile pavement will be little bumps before any crossing and lines which will warn you of danger.
General public is amazing, always willing to help. Since you're from the US, your cane will have a red stripe at the bottom. It might be worth thinking about getting an all white one as you may be mistaken for deafblind. Red and white here means both visual and hearing impairment.
Dating scene... Not a clue but best of look mate!!
I feel like I did a shit job at answering your question. Let me know!

Not here to answer anything, since I am not from Britten, but, there's Youtuber, Lucy something, from UK, her videos might provide some additional info.