Depends on two things:
1. Is your bsc focussed on pure, or applied maths?
2. Do you feel you have the sufficient knowledge to get a job doing something you enjoy?
Question 1 is because a degree on pure maths is excellent for doing research, but if you want a job in say operational research or data analysis, you may want to consider a masters degree in said area. However, if you want a job that involves pure maths (cant think of any off the top of my head but I'm sure they exist), a masters may not be needed.
Question 2 is because masters degrees are VERY varied. My maths masters is operational research, very very different to pure maths. Also, an msc in "mathematics" in some universities will remain pure, in some will contain lots of studies on cryptography, operational research etc. Basically, Msc in Mathematics is quite an umbrella term and you definitely want to look into several options for it.
Also, you may not enjoy an industry job life, and you may instead want to go into researching entirely, in which either a masters, or even straight to a PhD is plausible! You definitely want to have a chat with your personal tutor on this.
In terms of difficulty, all I can say is the usual twaddle of "as long as you're motivated, it's definitely possible". Choose a masters you enjoy, and you should be up for it
edit:- for reference, my bsc was heavily applied, I chose a masters to enhance the knowledge, but I reckon I could very much get a job without the masters. This is simply because I enjoy learning (and need a year to decide what to do shhhh)