I do a standard trifle like most of you but also my posh version made in a large loaf tin. Orange jelly made with as little boiling as possible, with a tin of mandarin oranges, including juice stirred in and a layer of boudoir biscuits on top. Left to set, tin dipped into hot water and turned out onto long sandwich plate, whipped cream piped around bottom and top then decorated with a row of mandarins.
No one has mentioned HOT trifle, which I make in winter with sponge buns, half a pot of HM jam (usually raspberry) thick custard. Heat until custard starts to caramelize, serve with cream. Or much the same made with our own plums and flaked almonds on top.