I had a steaming row with my dealer about it in April. It wasn't the first time I'd raised the issue. All I got was, the undertray is secure, MG won't do anything, well these undertrays do break, so what, why do you want it flat anyway, and finally, maybe if you contact MG yourself and pay for it... In the course of all this I told them about the Aussie fix and even provided them with a photo from a forum member. Well that's probably something MG Australia has decided to do off their own bat, nothing to do with us, says he.
This was going in in parallel and mixed up with the steaming row about their failure to install R33 at the one-year service despite repeated requests in writing, giving reasons. Finally they agreed to book the car in again for the software update - in September! But when I got the phone call with the booking, out of the blue they said there was a fix for the undertray and they'd do that at the same time. Presumably I get what @YaR has.
I tell you, once this is done they will not see me for dust. I'm prepared to drive to Galashiels, 35 miles away, rather than put up with that patronising, supercilious manager for one more moment.