Elton John: Now go save the world.
Harry Hart: If I save the world, will you get me two tickets to your next show?
Elton John: If you save the world, I'll get you a backstage pass, baby.
Eggsy: We've got brains, skills, skipping rope?
Whiskey: It's a lasso.
Eggsy: Whatever.
Answer: Harry probably believed Whiskey told the Golden Circle where they were since none of them were followed. Then there is also that Whiskey shoved the antidote out of Eggsy's hand he started to suspect he did it on purpose.