I'd be pretty pissed off if I were you. They should at least offer to replace it with the specification that you ordered and also turn that round as a matter of priority. I bought one of the base camp bags in the last sale and it took about twice as long to arrive than they quoted. But they did send me the bag I ordered and it is a brilliant bag, so kind of worth the wait.
I pitched my Trailstar outside and seam sealed it on the outside, thinning the Silnet with a little white spirts. Pay close attention to the seams at the apex as I found that the walking pole and pressures caused the stitching holes to open a bit more than elsewhere. I just ws a bit more liberal with the sealer in these areas.