Place approx half the sponge cake in the bottom of a glass trifle bowl or other pyrex style bowl

make up jelly according to instructions on packet(s)

Pour the jelly over the cake until it is soaked and sloppy

leave to set

Make the custard according to the directions but use a little more powder to get the right consistency. It should not be too thin otherwise you'll have sloppy trifle. Too much and it'll be too thick. Allow for the fact that it can set firmer than it will be in the pan.

Pour over the set jelly/sponge mix and leave to cool in the fridge

Whisk the cream until firm and spread over the set custard n jelly mixuture

Add sprinkles

Variations: Try raspberry jelly and chocolate custard. Just add  a tbspn of cocoa powder to the custard powder

Put fruit cocktail or salad in with the jelly

Add a dash of sweet sherry to the sherry sponge mix

Almond slices on the top of the cream is nice