Okay see I'm of the opinion that it's a natural plural; Traditionally the buggers are solitary creations and a closer rendering into English of the Hebrew plural (based on the rendering of the singular, a phonetic, ish, rendering, since I don't know if the symbols work here, would be Glem or Glim) would be Golemin and that's better than simply bolting an S on the end but still sort of inelegant.
I agree there is much missing from the book in the adaptation of Going Postal, still I hope the upcoming Watch series (if it's actually happening) is a development from the style and approach Going Postal more than anything else.