I'm pretty sure that unless they changed something you need to be level 40 to raise all secondary skills (cooking, fishing, and first aid) past 225. The artisan first aid trainer is in theremore isle for aliance and hammerfell for horde. All secondary skill artisan trainers require you to complete a short quest. The first aid one requires you to heal a number of soldiers that are hurt to various degrees using special bandages. Also, I'm not sure what the skill required for heavy mageweave bandages is, but I believe the skill is aquired through a book. It's been a long time since I've done it on my main, and I haven't aquired anything past regular mageweave on my rogue yet.