I live in Birmingham England and I dont know where I can purchase these cake mixes, Has anybody used these box mixes to make wedding cakes? and is it firm enough to take 3 tiers of fondant?
I personally think that DH is weaker than betty crocker so that's what I've switched to. I personally wouldn't use it for a 3 tiered cake. You could try lowering the amount of water to 1 cup and adding an extra egg per mix. That may make it strong enough to use.
I only use DH and have made plenty of 3 tier cakes and they hold up great.
I also use DH and have never had a problem stacking it. Have a friend who also uses DH, and she is able to stack them without a problem, too.
I only use DH as a base, I'm just not to fond of BC or Pillsbury. Also my good friend has food allergies and DH is the only one she can eat. You can technically stack anything with the right support.
Getting to the rest of your question, this subject was brought up here a few times, but long ago. It's rare to find those cake mixes in the UK. I hope someone from that side of the pond can help you, but you might have to resort to baking from scratch, instead.
Is there a particular flavor you would like to bake? Check in the recipe section. Almost all the recipes there are tried and true.
I use DH all the time, no problems here. My customers RAVE about the look and taste of their cake. If it' ain't broke, don't fix it
I only make wedding cakes for family, and because my scratch recipes are too moist and don't cut sharply, I use Duncan Hines. I am very inexperienced with wedding cakes. I made a four tier cake in May with each tier about six inches tall. The cake held up perfectly and I LOVE Duncan Hines taste. I scratch bake because I love the science of it, but DH is in my pantry too.