Hi i need a really good 3D UK recipe for a 3D cake i need to make. Has anyone from the uk got one please?

If you mean you need to carve the cake then its a maderia cake you need then freeze it before you carve I use Lindy Smith recipe for mine.

Do you layer and fill these before you carve them, or just carve the plain cake?

ALayer and fill then chill till firm enough to handle. This minimises crumbs. Then take out of fridge/freezer and begin carving to desired shape. When that is achieved; you can then crumbcoat and chill for a bit more before covering with fondant.