What you have to remember at these stations is SE100K is what Air Canada recognizes you as, and star gold what others.

Aspire are not affiliated to anything *gold.

It is true that at places like Glasgow and Dublin where lounges are not common (there might be one) people like United negotiate contracts to allow certain customers into the lounges. If you read the small print though, only Business travellers are given this exemption. United 1k members for example are not included.

Out of Glasgow, AC only flies Rouge and therefore doesn't have any business class passengers therefore there is no recourse to allow entry.

In this case, you were rightly denied access to the lounge, AC has no obligation to try and negotiate for some of its members to be allowed in, and would probably not be successful anyway.

Sorry to be blunt, but that's all there is to it really. Being SE100K has nothing to do with anything really.