I have been a self employed bookkeeper for nearly 27 years when I was made redundant the day after I found out I was pregnant with my first child. Scary times! Over the years, all my clients have come to me through word of mouth, so I must be doing something right! Be very aware that if you advertise as a bookkeeper, you will need a practice licence AND professional indemnity insurance, even if you don't have a client. This is because you are offering bookkeeping services.
You don't have to offer SATR. I actually only do returns for 4 clients (out of 16). I make a decent living out of doing bookkeeping and payroll.
I'm out in my clients offices 3 days a week. There rest of the week is spent working on the smaller clients books.
I hope this helps!