Many people have built up a successful cleaning business by starting as a self employed cleaner and then as the business builds up, employing other cleaners and once you have enough clients, you won't have to do any of the cleaning yourself, or maybe just for holiday, sick and perhaps maternity cover, so you earn your salary by the difference in the hourly rate between what your clients pay and what the cleaners earn, not from hiring yourself out as a cleaner.
However, you'd need quite a lot of clients to get to that position. Did your previous business employ staff or was it just you?
There's a lot of advice about employing people on the HSE website for health and safety obviously, eg risk assessments and the HMRC about tax and NI for employers and employees and the differences between employing cleaners and being an agency for self employed cleaners, although a lot of 'self employed' agency workers only hold this status so their employers can avoid NI and employment rights and HMRC are cracking down on this, so it's best to avoid that route from the start.
Definitely work as a cleaner first if you've never done this as a job so you learn what is a professional standard so you can do end of tenancy cleans, which I imagine can be quite lucrative, and also how long it takes to clean effectively when you're having to do it fast enough to earn money at an efficient rate, not just keeping your own home clean in your own time. Might also get an insight into how other agencies work so work so you can gauge good and bad practices and if you end up charging what seems like a high hourly rate, be able to explain why it is that high, because you don't cut corners that others do, eg cash in hand, false self employment. Also look into rules for making sure people have the right to work in the UK, especially after Brexit.