Raw Input 
12345678901234567890123456789012
John Smith   753 967Citroen C2
Peter Brown 133 329 Benz E320
James      103 7482 Citroen C4
Desired Output 
12345678901234567890123456789012
John Smith 753 967  Citroen C2
Peter Brown133 329  Benz E320
James      103 7482 Citroen C4
Script and Comments
Script1 
[ 1] s/^(.{11})(.{9})/\1\n\2\n/
[ 2] s/\n( *)(.*)\n/\2\1/
Comments
  1. The `-r' option of GNU sed must be used or you have to escape every left and every right parenthesis used to capture texts.
  2. Step [1] inserts a newline character at column 12 and 20, respectively.
  3. Step [2] moves the leading blanks from after the first newline character to before the second newline.