Investing as a US citizen in the UK

Hi,

Apologies for the not-so-exciting topic.

Does anyone have experience or knowledge of investing from the UK (ie. live/work in London) as an American citizen?

I've struggled to find clear direction through Google and would prefer to avoid paying a tax/investment specialist if possible. But essentially the issue is that the US decides to tax their citizens even when they're abroad, so I don't believe I can invest in funds unless they have a certain registration to US and UK regulators? But I've read elsewhere that I can invest in individual stocks without an issue.

What can I invest in? Will I be required to file my earnings?

I'd appreciate some more info on all of this because it isn't particularly clear anywhere..