1998 Vauxhall Tigra are certain parts for a corsa compatible with a tigra?

Yes, many Corsa parts fit the Tigra. But...(there's always a "but", isn't there?)you will have to double - check each part, if you are planning to swap parts between the two models.

GM changed parts suppliers for many of the ancilliary components (radiator, alternator, etc) very frequently on both Tigra and Corsa models throughout their production. In general, both cars are mechanically identical with important detail differences. Basically, the Tigra is a Corsa with a cute body but that is kind of an over-simplification; not all parts are swappable between all models. A camera and an eye for detail will help match second-hand parts.