Agreed, there’s no way that’s happened to new metal in a couple of years. Those BMW-style jacking points are terrible rust traps.

These pictures are terrifying! I'm just after moving from a 100% rust free disco 3 to an L322 with what looks to be a very good underbody but you never really know until you start stripping back the plastics.

On the disco I used a product called Rust Bullet, have you guys ever used it? Ill be doing the same to the RR in a few weeks. Its a 2 part product. First you paint 2 coats of a rust neutraliser and inhibitor paint which hardens unlike a lot of under coat. You then spray a black top coat which is you barrier from salt and UV etc.

The website is pretty crap but there is lots of info. Ill try and post a picture of the underneath of the disco post treatment

This is the IRL agent, Im sure someone in the UK distributes too
https://www.rustbulletireland.com/

FLA:

Its definitely an issue but not one that you should be too afraid of. If you remove the plastics from each side (there's a dozen or so clip type fasteners, some may need replacing as they can be a bit brittle, this is a good source: https://vehicleclips.co.uk/collections/lan...fasteners) - then you can at least see what's going on, takes maybe 10 minutes to get them off.

The weak spot is the rear sill around the jacking point and often starts to show on the very bottom of the arch before it disappears below the plastics. The problem is that by the time you notice up in that area its probably already eaten away quite badly at the bit hidden by the trim. I wonder whether this is the problem the OP had and the cause of the issue was not addressed properly.

What happens next is very dependant on what you find. There are options for just patching it up with fresh metal, replacing the whole rear section (at the extreme end), or if you catch it early enough just giving it a bit of love.

My car has had the sills repaired in that area (2007 car) and the rest of it is not very bad at all, just some surface rust in a couple of places but nothing you would not expect.

Good luck with it.

Added for reference:

https://www.fullfatrr.com/forum/topic65295.html?highlight=sill

https://www.ebay.co.uk/itm/285220129776