I was surprised by some of your comments about the Sarissa buildings.
With exceptions (see below) I have been very happy with most of the Sarissa buildings I have assembled.
The instructions are generally clear, and I do not remember having difficulty identifying components, and (unlike most other MDF kit suppliers) they have been supplied in all the kits I have bought.
I have mislaid the instructions for the Survivor Shack, but you can see the instructions bottom left for the Russian Outhouse.
The instructions for the TWD:AOW buildings are extremely detailed.
I do, however agree with your comments about the grey board roof - it is not very good. I reinforced mine first with PVA, and then went for a tar paper effect with tissue paper applied with PVA. In the end (and after consultation here) used Slater's 4mm scale corrugated iron secured with epoxy.
The Jersey and Texas barriers are very difficult to make a good job of, as are the GOA ore containers. The TWD:AOW RV uses greybeard overlays and I have nearly given up on it. The greybeard appears too hairy for metal sheeting, and getting it round the various corners without tearing I found very difficult.
More examples of Sarissa buildings here:
https://ultravanillasmurf.blogspot.com/search/label/SarissaI certainly think the Sarissa buildings are generally worth the money, and I look forward to seeing how you fare with the ones you have bought.