All ads for the airline will now include the fee, but it sounds like they’ll down play things by breaking down the price based on assumption of you traveling as part of a four person group—like a big ol’ happy Chevy Chase European Vacation family. Still it’s just one fee per reservation, so you’ll only be hit with the £9 fee once whether you’re flying solo or with the whole crew.
In order to figure out things for yourself it’s often best just to go through the whole booking process—just leave the credit card in the wallet until you’re ready. That way you can usually see the breakdown of what goes where to get you where you’re going. It’s much easier to click to a new window than to request a refund, because you know that money is never coming back to your bank account.
Just remember that there’s still a handling charge to cover processing costs when using your credit card, so maybe just stick to the debit payment instead or pay in cash—ha, like that's possible anymore.