Eggsy's head falls back a bit. He holds on for another few moments, only because he doesn't want to ask. He doesn't want to give that weird kink away to someone else. This was, of course, Dorian's actual plan. It was never really about what he says to Dorian when they're alone. He hates it, but he also doesn't hate it, and that's worse.

"Fuck, please," he says, "please let me come, Daddy."

Quentin has no way of knowing it's a spell, that Dorian will hear it from wherever and grant permission, and Eggsy isn't about to go into it. All he wants to do is get off. He'd rather do it on Quentin's dick but this is more than fine.