Hi, while since I've seen you on the board. I use NGK plugs in my 1100GS and I think that they are much of a muchness with the Bosch plugs that I've used. I use the NGK plugs because they are cheaper than the Bosch ones but last about the same length of time.
Regarding plugs, I've noted that the 1100GS I have is hard on plugs. At about 7,000 to 8,000 Klm's it starts to miss slightly at very low revs. So I put in new plugs and bingo, back to normal again.
I'm running NGK 2095 (outside of plug box number) on the actual spark plug it says, BKR7EKC-N (NGK R) The NGK R is with the R under the letters NGK and the R is underlined.
I get these from the Victorian BMW MCC spare parts officer.
Mick.