As a recent bride, and having been to the National Wedding Show before (be it the London one of the same show), I would have chosen the BHS dresses and the lingerie, given the choices they had.
Ian Stuart dresses are "dreams". As Raef said, very high risk strategy, but I knew as I watched it that they would likely only get a couple of sales, and only towards the end of the day. Kavanaugh is spot on with the reasons why. But that's all they needed to win anyway. As for the lingerie, it's a perfect choice for a wedding fair. When I went, I only ever bought small things that the groom wouldn't be interested in and that didn't cost too much. So as soon as I saw both items I knew that provided they got even just one dress sale, they were likely to win. I mainly viewed each wedding fair as an information-gathering excercise.
Coloured dresses - interesting idea, but not mainstream. Wedding fairs are for mainstream customers I'm afraid! If they were bespoke, by a very well known designer, and more expensive, the idea is great, but they looked cheap and no one wants to look cheap on their big day - there are plenty of designers out there who can design beautiful pieces without the Ian Stuart design tag and BHS were a perfect example of that. I would definitely have gone with that as a safe bet, but only if the other team did NOT go for Ian Stuart, as if that had happened, I'd wave the white flag before even starting, knowing that they only needed a couple of sales to win whereas I would need about 30 to even come close.
Cake is a big no no nowadays. With weddings being so expensive, it is rare that you will find a "normal" budget bride who considers the cake to be worthy of spending so much of the budget on. For mine, I just had an M&S cake, but spent a bit more on a personalised topper - something I can keep! If THAT had been an option in the Apprentice, I would have gone for that - toppers instead of the cake itself.
Jewellry and shoes would also have been a fab addition to the dresses.