The UK apron is only 7-9" wide. And the sides are parrallel. So no tapering required. Also there is no defined Fell line, no Steeking and no liner.

They are designed to be made in under 4 hours. (it takes me a day to duplicate one)

The edges of the pleats are straight and the only tapering is to tack down each pleat to the one behind it on an angle.

There is no need to get technical in your tapering. There is no need to worry over details.

A UK styled kilt should be made VERY large. It should almost fall off you without a belt. This makes tailoring and fitting very easy as there is none.

As long as the hip area is about 4 to 5 inches loose and the waist is 2 to 3 inches loose you will do fine.