drylining (dont know if you know but) put blobs of adhesive on the wall and not the board , usually 4 blobs accross the 1.2m board , put a little ofcut of board under the board on the floor (makes it so much easier when knocking it about) and with a 6ft straight edge or similar (can use a level) bash it in all directions or where it needs it to get it flat/level ,
all fairly simple
and let me know if you want me to have a look stu , next time im oooop norf
