I have just uploaded the Haynes Vauxhall Vectra manual for facelift 99-02 model Vectra B's.
Although its for facelifted models, the vast majority of the information is also useable for prefacelift models. The most notable differences are with wiring, engines and transmissions. Body, interior and exterior instructions should be near enough identical.
The PDF is available for download
here. Due to the size of the file, I strongly suggest you save it, then open from your local drive. It will likely crash your web browser as the file is 100mb in size.