Does a 1998 Vauxhall Vectra 2.0 DTi LS have alarm and immobilizer fitted when built?
The answer is yes.
This information can be found in the article that is titled "Vauxhall Vectra 2.0 DTi LS (1998) review". Within this article, there is a section titled "Security" that states the following: "Thatcham 1 alarm and immobiliser as standard".