I'm going to start my son on solids next week. He's currently on 5 milk feeds. Do I drop a feed as he starts eating solids?

Nope, baby's main source of nutrition would still be from his milk. For my son, he gets his pureed fruit/vegetation about 1.5 hours after his milk then I'll give him a bit of water (30ml). You can read more here to have a better understanding. http://sg.theasianparent.com/good-complementary-feeding-routines/