I've seen some covers by Lseat, bu not their 911 offerings. The quality seems decent, especially for the money. The biggest issue I see is with color and texture matching. they have a very limited choice, with nothing anywhere close to my 911's brown interior or the burgundy from my previous 928. If they had a close match I would have given them a try.
I've heard good thing about World as suggested by creaturecat.
I went with
Classic 9, and have been very happy with their work.
For the 911, I had them recover my leather dash, make seat covers with Pasha inserts, and new door panels with added Pasha as well.
My current 928 has Classic 9 (installed before I acquired it) dash, center console, door panels and carpet kit.