lwb series 2a station wagon rear seat x member

I've just bought a series 2a 109 Safari station wagon, its in great condition, however the cross member that sits beneath the rear tub, directly below the rear seats, is rusted out. I have been told that this piece just bolts /rivets in place, and can be fitted by removing the small section of riveted body panel adjacent to this, does anyone know if this is correct. Also any ideas where I can get hold of the replacement member.