So many great songwriters in the 80s that were also writing great songs in the 60s, 70s, 90s, and now (e.g. David Bowie). For songwriters generally associated with the 80s, however, I might also add in no particular order:
-Andy Partridge (XTC)
-Chris Difford/Glenn Tillbrook (Squeeze)
-Mark Hollis (Talk Talk)
-Bryan Ferry
-Danny Elfman (Oingo Boingo)