If it's a genuine MOD kilt with the arrow stamp on the tag, then yes it should be well-made. Condition, on the other hand, can vary greatly. A lot of them have moth holes in the under-apron, straps are dry and cracked, pleats a mess, etc. So you really have to pay attention to the photos you see, and be prepared for there to perhaps be something that needs attention.

Is it a newer surplus kilt or an older one? Are you sure it has military box pleats?

The MBP kilts can be a bit of a pain to maintain the pleats on. They can tend to curl out due to the fact that the outer "rolled" portion of the pleat isn't held in place by adjacent pleats like a knife-pleated kilt. And they are much easier to mess up from sitting on them haphazardly for a long period. But if you pay attention to sweeping the pleats and give your kilt regular maintenance such as pressing, it should last a long time and look grand.