I didn't know what to do with.

There is concern about corrosion that can occur in Nissan Terrano or Nissan Mistral vehicles of the type whose rear floorpan assembly consists of a two-layer (double-skin) panel. If moisture gets trapped between the two layers of the floorpan, corrosion can occur around the seat or seatbelt anchorages, affecting their integrity. Corrosion can also occur where the under-floor reinforcing panel overlaps the top floor skin

installation of the LVVTA rear floor load-bar seatbelt anchorage reinforcement system together with a Low Volume Vehicle certification plate containing the following words in the Body/chassis field: ‘LVVTA Rear floor load-bar seatbelt anchorage reinforcement system.

Removing body rust can preserve the integrity and appearance of your vehicle. To do so, first identify the type of rust on your vehicle and equip yourself with the right tools to get the job done. You’ll find the goods you need here at Raybuck. 

Hi you are probley all aware of the rusty double skinned floors in the Terranos,my question is there any way to prevent it happening in the first place as I plan 2 go off road quite a bit in mine??? 

Common problems with the TD27 is the water pump, valve gear and EGR.

Water pumps tend to corrode the housing, use good anti freeze.

Rocker shafts and rockers tend to ware quite easily if the right spec oil isn't used for the Jap diesels, high magnesium content in oil required.

EGR tends to clog the intake manifold and make it smoke, especially when hot and left to idle for a while.

Other than that, they are as bullet proof as the turbo charged TD42.