I hope it is covered by the warranty. According to the removal & refit guide document on
@siteguru's website the proper way to remove it is to remove the spoiler or lighting bar on the boot lid (SE has the spoiler). For the spoiler at least I know this involves taking off the boot lid trim.
At a guess I would think an MG tech would take 15 minutes to remove and refit the lamp. I suspect it would take me the best part of an hour and I've removed the spoiler before. If you have to go down this route, take a look at @DevonMG's video guide to fitting a rear camera part 2.
Looking at the above doc it shows the lamp assembly from the inside of the spoiler and mentions removing a clip. It's not easy to tell if removing the lamp from the outside is possible at all and if so how difficult it might be.