Yes, the wall will be behind the wardrobe from both sides.
There were 2 wardrobes before but no wall in between.
Yes, it's a 45mm stud with single plasterboard only.
Old studs that can be spliced together more easily, maybe it was common in the past.
I don't think it is a wooden board but will double-check.
Will check with them how big the wardrobe will be, maybe the wardrobe covers the splice if the old plasterboard is not removed.
Thank you