It depends a lot on you, where you want to study and what you want to study.
You say you want to boost your CV - if you are trying to cover up poor grades then an LLM is a waste of time - it won’t make firms ignore a 2.2, and you may not have the academic ability needed for an LLM if you have a poor LLB.
If you are doing it becasue you don’t have a TC and you don’t want an empty year on your CV - don’t do the LLM. Get a job as closely linked to law as you can find, maybe even volunteer for a few months.
Doing an LLM at Oxbridge is better than doing it at an ex-poly (if you decide to do it).
Make sure you are doing it in a relevant area - e.g. if you want a city TC don’t do an LLM in child care.
Mac64 is an exception to the usual LLM process - very few firms will pay for an LLM (whereas many firms pay for the GDL and LPC - surely that’s saying something about the value of an LLM….)
I would say that as you are unsure if it is a waste of money, err on the side of caution, save your money and do something else with it!