I’ve done two MAs - one when working full time with young children, and the other when I took early retirement. Different subjects (both different from my BA) and different universities but even so there was no comparison.
Studying around work and children is very hard work, but doing it with no other responsibilities is very different, and more enjoyable. Also, my first one was for work and whilst I was interested in the subject it was really a case of getting through it, and I had to be strategic about things like reading lists so that I could fit it all in. The ‘fun’ one was different, and I went to lectures on modules I wasn’t even taking as I had time and enjoyed it so much.
The standards are higher than for a bachelors degree, and there is an assumption that you know more than you might do if your first degree is in a different subject. If there are gaps in your knowledge it is absolutely up to you to identify and plug them yourself or you will fall behind.
The upside is that everyone on the course will be highly motivated and that really helps. On both of mine there was a high percentage of older students- more than 50% in the last one, so you won’t be alone or out of place.
Enjoy it - after being at work it will probably feel slow paced, but the time will go faster than you expect. Oh, and think about your dissertation from the start. Coming up with a title and focus can take ages, so the sooner you start looking out for what might work for you the better.