Why should apple replace the film. It didn't come witht the phone. How about apple charge the op $15 for returning a modified phone.?
This point is as valid as that the OP is making, imo. I can't understand how the OP feels he's being 'cheated' out £15. Fair enough, the guy in the Apple store recommended it, but let's be honest, he's probably trying to manipulate his accessories as a percentage of total sales to make target. If the OP bites, that's good for the employee, and the OP gets his screen protector.
Why Apple should cover the screen protector, sold as an accessory to the purchase, and produced by an entirely different company, is beyond me.