So... the first thing to be aware of is that generally MSc "conversion" courses (that I have experience with) in IT/CS have a pretty high drop out rate. They are very intense, but definitely do-able.
Regarding employment prospects: Employers are more savvy to "conversion" masters in IT/CS now. They know that generally it's about 50-60% of the content of an BSc/BEng in IT/CS squeezed in to one year. I've interviewed conversion grads from QUB and Ulster Uni and I've found them very much a mixed bag. Those who excelled in the course were usually very good. Those who just passed the course we found to not be a great fit for the company. The last thing the tech sector needs is mediocre coders or people who only half understand tech or who "just want a cool job". Recently companies (in Belfast anyway) have shifted their focus on to CS undergrads and are focusing less on Masters conversion students. Generally CS undergrads have more of a passion, understanding and generally just more education around CS so you get a better return from them.
Regarding Cyber Security: This is a huge field and you could do an undergrad, masters and PhD just in it, and if I'm honest you'll only touch the surface of it in a conversion course. With that said, if you are aiming for government roles, you'll be in luck as government are so far behind the curve with cyber security (I mean terrifyingly behind the curve) they will take people with any kind of experience or education in this area at the moment.
Workload: You cannot practice coding enough going in to these types of courses. At masters level, you have to do a lot more independent study and you will do 90% of your coding outside of class. Form a good group in class is my advice and practice practice practice between now and September.
Good luck. You can definitely both succeed.