I would replace the IMG
Yes, they are not expensive and often a reason for coolant loss.
The OP has done the right thing in seeking advice.
My Prime Suspect for that kind of coolant loss level would be a worn or wearing Water Pump. Could be other reasons of course.
How to check for a worn, leaking Water Pump? Look for stains on a dry, cold engine or wetness on a recently switched off hot one. Look below the Timing Belt Plastic Cover at the right side of the engine. Best viewed with the front wheel arch and ideally with right wheel removed. See attached image for where to look. Coolant stains or wetness on the alloy sump area below the large pulley in the picture are the signs of a worn, leaking water Pump.
As previous posters rightly advise, coolant loss invariably leads to other engine damage due to overheating ... in any car. Need to ID the cause of the coolant loss and rectify asap. If you draw a blank with your searches, best to seek advice from someone who really knows these cars. Not all professionals do.
My MG ZS120 bought new eleven years ago has been faultless. However, I do keep an eye on things and check regularly as all car manufacturers recommend users should do.
Far too many car users freely admit to never ever lifting their bonnets or even check tyre pressure with safety in mind unless something goes wrong ... Guess what... It don't work like that ...
... so something goes wrong. The previous owner of your car could have been of that mindset.
In the picture of a lady friend's car are the minor first signs of a leaking worn pump. Just a little at first then gets worse with more miles and wear. Then suddenly it lets goi and a river of coolant soon is lost.