Wedding cake.
The final cost depending on the size, filling and decorations:
4-6-8 inches from £230 approx 70 portions
6-8-10 inches from £310 approx 120 portions
8-10-12 inches from £430 approx 180 portions

Two tiered cake:
4 and 6 inches from £110 approx 30 portions
6 and 8 inches from £200 approx 60 portions
8 and 10 inches from £300 approx 100 portions
 
Mini tiered cake 7+5+3 inches from £200
 
cake portions (1x1 inch)
 
On top of that, we can add the following optionals:
⁃ 10 Buttercream roses or 10 macarons : £20
⁃ Swiss meringue buttercream: from £50 (depending on the size of the cake)
 
I would recommend at least the Swiss meringue buttercream because the flavour being more silky and smooth than a regular buttercream.

About the cake and filling combinations, here are some examples:
Vanilla sponge, soaked with vanilla syrup, vanilla buttercream and strawberries or raspberry; 
Lemon sponge, soaked with lemon and Limoncello syrup, layered with lemon curd and lemon buttercream;
Orange sponge, soaked with orange and Grand Marnier syrup, layered with orange marmalade and orange buttercream;
Rich dark chocolate cake layered with chocolate fudge buttercream;
Rich dark chocolate cake layered with vanilla buttercream and mocha buttercream;
Pink Champagne cake, soaked with Champagne syrup, layered with vanilla buttercream and strawberries.
Red velvet cake, soaked with vanilla syrup, layered with vanilla buttercream.
 
MADE IN A KITCHEN WHERE NUTS, GLUTEN AND OTHER KNOWN ALLERGENS MAYBE PRESENT.
NOT SUITABLE FOR PEOPLE WITH FOOD ALLERGIES BECAUSE ALLERGENS MAY BE PRESENT IN THE ENVIRONMENT IN WHICH THEY ARE MADE.