Has anyone done the process of starting an LTD to trade stocks in the UK? What is required?

I have stocks into a personal account. As you can imagine, if I want to sell and buy during ups and downs, I’ll have to account for tax every time I make a profit, even though this is fully reinvested immediately. Given the above, I want to start an LTD (UK) to better manage my investments. I have seen other people asking similar questions, but only on whether it is possible to trade through an LTD.

Has anyone been through the process? What are the steps? For example, I know that you have to register at the Companies’ House like every LTD. But there are some fragments of information that I cannot confirm, like:

1. Is there also a process with the FCA I have to consider?
2. Is there any process or registration with the London Stock Exchange? I read somewhere this is required and also gives you access to IPOs. Do I have to do similar process per Stock Exchange I want to join? Example, in the US.
3. Do I need to use a human broker whenever I buy/sell through a company, or can I do it via a platform?
4. Any costs associated with the above?
5. Any other advice, tips, etc?

I have already asked HMRC and ICAEW but they didn’t give any useful information. HMRC said what I already know re Companies’ House and ICAEW just told me to find one of their registered accountants. I did contact a couple but they haven’t done it before. Also awaiting response from the FCA.
All advice and guidance welcome. Thank you in advance.