I can't answer for sandfly, but I often use the real thing glued together with craft bond adhesive spray. I like the long stick caddis and the grannom wood pulp case (the pebble cases always break when detaching from the bottom of rocks, plus they are stuck fast, so how much washing away really happens with them to be available for trout).
For an imatation case, I use turkey tail and for the insect itself, I use caddis green micro chenelle. I place lead on the shank, Burn the end of the chenelle and tie it extended over the eye of the hook. The I add legs (black saddle hackle or partridge). I then wrap to the back and tie in a 1/4" section of turkey tail. After wrapping the turkey forward I coat it in felximent.