From what I have seen many of the Vauxhall re-maps are done the way Stu has described how this BMW map was done, that includes some serious engine builds with 450bhp-550bhp as well as standard spec 'go faster' re-maps, many have the standard safety functions disabled or a value of zero to stop the warning light on the dashboard from showing.
Some of the high profile companies with 'good' reputations, not just in the Vauxhall world re-map this way.
Good luck.

Steve