Something has gone wrong and I can't figure out what it is, this isn't the first model that I have made for Oblivion but it is the first armour piece, and it just won't work! The entire armour piece above the waist becomes invisible, leaving just a belt and a small skirt like bit covering the waist and thighs, I thought it was probably a problem with the model so I tried just retexturing the chainmail armor as it was basically the same model anyway, but still only the thigh guards come through, all the properties are the exact same as chainmail armour now other than the texture, yet it won't work. Somebody help me please. Also, the full model including the cuirass and arm pieces appear in NifSkope, the texture is .dds.

Couple of possibilities :

1-- if you made changes to the NIf you might have messed up the skinning/weight painting of the vertices (probably not your problem if you didn't change the NIF)

2 -- Most likely your problem is that you forgot to also make a copy of the normal map for the texture (_n.dds file) --- The normal map is used for light reflectivity and without a normal map no light will reflect (thus it appears invisible) - so make sure you have the normal map made and placed in the same folder as the .dds texture and with the same name +the_n.dds extension

3 -- If you made a normal map - you may have made this error --- using an _ in the name -- the game will truncate after the first _ character so a texture named My_Texture.dds would need a normal map named My_n.dds in order to be found not My_Texture_n.dds !! (this can be useful when wanting several versions of a nif to use the same normal map (ie various colored versions of the same object) so you do not need a seperate normal map for each color !)

I think your right, probably is the normal map, but how do I apply one?

EDIT: just read it again and realised you already said it

Thanks for the help JDFan, got it working now

No problem - glad it is working now !