The terminators are unnecessarily slow. All termis have force swords and 2 attacks. Therefore they need to go last and possibly die before attacking? Demon Hammers are great but they are not necessary, especially in that great numbers. Half a squad does not need them. Replace the hammers with a brotherhood banner psibolt ammo and give everyone you can afford halberds. 2 attacks normally per termi at i6 is fearsome, especially if they are power weapons and every wound kills a model no matter how powerfull with 2 exceptions. 1)EW 2)invulnerable saves, although these can fail easily too.
You also MIGHT want to ditch some purgators, you have too much heavy weapons.
One last thing, get transports. Unless its a small field you need transports. Alternatively you could get a librarian and deep strike and hope he doesnt die before summoning everyone, but this is a bit too dangerous. Deep strike and speed are grey knights greatest weapons. You could even do that with purgators and open fire behind lines b/c you can shoot after striking in.
Also (I forgot...) give purifiers halberds, even over termis b/c they only cost 2pts for the same thing, then go to termis with extras.
If you go down to the woods today, be wary