I've fitted an £8 set from China with no problems, no drilling of body/metal- just the rear bumper. It is an art to line up the 4 of them centrally and once you have drilled the hole- thats that (if I'm honest, one is slightly too high). i used a piece of string taped across the bumper to give me a straight-line. then equally marked/measured the pilot holes.
I mounted the speaker/tone unit in the boot and i can hear it (I'm old and a bit mutton) but if music is on the wireless (I did say i was...) then, i just turn it down . if someone is talking (usually my son, but now he drives the problem has gone- i just used to tell him shhhh- Dads reversing!)
Some non-MG folks took the mick that I bothered with such a small car- but believe me- it will save little knocks and park you closer than you dare!
Other modes of transport.
Range Rover Sport