The James Martin one only serves 20/30 people, so because of the way it looks, not sure if you would be able to do larger quantities/tiers.
But I have found this one - you could make tiers for it
www.goodtoknow.co.uk/food/138379/White-chocolate-celebration-cake
and here is Mary Berry's American Chocolate Wedding Cake -
30 eggs separated
8 whole eggs
21b 13oz caster sugar
31bs 9oz good quality plain chocolate broken into pieces and melted
11b 14oz ground almonds
7 and a half tsps black coffee
8oz apricot jam, sieved.
Icing
2 and a half 1b plain chocolate broken into pieces
11b unsalted butter
To Decorate
foliage and flowers
Pre-heat the oven to 190oC/375oF/Gas 5. Lightly grease and line a 6 in, a 9 in and a 12 in deep round cake tins with greased proof paper.
Measure the yolks, whole eggs and sugar into a large bowl and whisk until thick and light. Add slightly cooled chocolate with the almonds and the coffee.
In a separate bowl, whisk the egg whites until stiff but not dry. Fold carefully into the chocolate mixutre, then divide the mixture between the prepared tins.
Bake in a pre-heated oven. The small cake will take about 45 mins, the medium cake about 1 hour and the large about 1 and a half hours (cover loosely after 1 hour). They can all go into the oven at once, large on the middle shelf and the two smaller cakes on the top shelf. Test the centre of each with a skewere which sould come out just about clean. Turn on to a wire rack to cool completely. At this point, the cakes can be frozen. Turn the cakes upside down so that the flat side is uppermost. Brush over the tops and sides with the warm sieved jam.
For the icing, melt the chocolate slowly in a bowl over a pan of hot water, add the butter and stir until the butter has melted. Place each cake on a cooling rack with a baking tray underneath to catch the drips and pour over the chocolate icing. Smooth the top and sides with a palette knife and then leave to set in a cool place.
Place the largest cake on a board or serving plate and stack the other two cakes on top. Decorate, in situ with fresh flowers and foliage.
It does say you need huge bowls to make this cake. The icing should be made the day before the wedding otherwise it will lose its sheen.
If you want to try the smaller cake out first - here are the quantities
3 eggs separated
1 whole egg
5oz caster sugar
6oz chocolate
3oz ground almonds
half a teaspoon black coffee
2 tblsp of apricot jam
Icing
8oz plain chocolate
3oz butter