Hello all ive nearly completed my m113 theres not much left to do ive completed the main body and all the sub assemblies and sprayed most of it just a few bits left but i was just wondering what do i do next do I put the decals on then spray on the matt varnish then weather it or do i varnish then decal then wether please help.

If your done with your painting I would put on a coat or 2 of Future, then do your washes, then decals, then a flat finish.

I'm not sure if the varnish that you refer to is a replacement to Future maybe someone else can help here.

Gloss coat, decals, wash, matt coat. You want to have the washes help blend the decals into the rest of the model. These markings are painted on before deployment and the weathering process would affect them as it does the rest of the vehicle.
Consider...you put the wash down and these nice shadows and panel lines get emphasized. The you add the decal and the panel line disappears behind the decal!