HL2 Models/Sounds not working

Right, I’ve had this problem for a while…
Every time I start playing Garry’s Mod it loads up nice and smoothly, but when I go into a game however (Singleplayer or Multiplayer)
all of the HL2 Weapon Models are missing (v+w_models and also I can only see the c_hands on c_models), most sounds are missing and basically it only happens whilst steam is online.

I’ve checked the directories and VPK’s are fine, validated my GMod, cleaned up my GMod. And I’ve also had fun with gameinfo.txt, still no luck.

I have been messing around with Source SDK for a while now, I’m not sure if that has got anything to do with it…

All my games are converted to steampipe, I don’t think it’s has anything to do with the problem.