If there is a hole through the floor or if you feel the damaged area will continue to deteriorate, this is how I would repair the floor. I will assume there are no obstructions under the trailer.
I would remove the floor covering inside the wardrobe.
Cut out the damaged area of the floor.
Measure the thickness of the trailer floor.
Obtain a piece of exterior grade (Not Treated) plywood the same thickness as the trailer flooring.
Check with local contractors for the plywood, they might have a piece of leftover plywood that would work for you.
Cut a piece of the plywood larger than the hole that you cut in the floor.
Lay the plywood patch over the hole and trace around it.
Mark the patch so that it will be installed in the same direction that it was when it was traced.
Cut the trailer flooring on the traced line.
Make sure the new patch fits the hole.
Cut a piece of plywood to cover the area inside the wardrobe where the floor covering was removed.
Use exterior grade deck screws to fasten the new plywood floor to the trailer flooring.
If the plywood is less than 5/8” thick I would also use construction adhesive.
If the trailer flooring is made from OSB (Oriented Strand Board), I would place the screws from the outside up through the OSB into the plywood.
Make sure the screws are not too long that they protrude through the plywood.
From the underside of the trailer, paint the area of the plywood floor that is visible through the hole and the cut out area of the trailer floor.
Use exterior grade primer.
Prime the new plywood patch, especially the edges. Remember not to cover the orientation marking that you marked earlier.
Secure the plywood patch with deck screws.
Neatly seal the gap around the patch with a good caulk that can be painted.
Try not to smear the caulking.
Use a good metal paint to paint the exposed screw heads.
Prime and paint the patched area.
Inside the wardrobe, if you are going to install vinyl flooring, I would fill all knotholes and large gaps with floor leveler.
Install new floor covering.