That's a bit crap. AIUI, the Brooks model (at least for Cambiums) is that you pay upfront for the saddle, and get given one that's marked SAMPLE in large, unfriendly letters.
Once you've made up your mind, you return it to the dealer, who exchanges it for either a brand new one, or your cash.
Given that Infinity saddles don't seem to be in any actual shops, I'd be inclined to go down the order and cancel route, which gives you a fortnight to decide, and all your money back. (Consumer Contract Regulations 2013, I think. They have to refund postage too, unless they've told you in advance that they won't.)