Gelatin also come in sheets like paper, though I’ve never seen them

Jelly:
The quantity given in the recipe is equivalent to two thirds of a packet of Chivers or Hartleys jelly cubes (8 of the 12 cubes). This amount should need to be made up to 383ml, but I’d suggest only, say, 350ml so the jelly is firmer for cutting.
None of my jellies was as vibrant as in the picture – I suggest a drop or two of food colouring to boost the colour, particularly the strawberry/red and the lime/green. Both companies make more flavours than are usually seen on any given shop shelf, but they must be available somewhere: blackcurrant, strawberry, raspberry, orange, lime and lemon; in addition, Hartleys make pineapple and black cherry.
I made the mistake of putting some of my jellies to set in containers which were too big and they didn’t make chunky cubes – you’d want trays about 21 x 14cm.
I don’t think there’s anything to gain by cutting them into chunks the day before. I got bored and left some until I was assembling and the were OK. The ones I did cut stuck together anyway.

Milks:
Our tins of condensed milk (Carnation or supermarket own brand) weigh 390g and contain 325ml. The recipe converts to 400ml.
Our tins of evaporated milk weigh 410ml and, being less dense than condensed, contain about 400ml. The recipe converts to 350ml.
The recipe quantity of ordinary milk converts to 563ml.
The total amount of milks in the recipe converts to 1,313ml. If you use one tin each of condensed and evap, you could make up the same volume by using 588ml of milk.

Gelatine:
The quantities in the recipe are equivalent to 3.3 sachets of Dr Oetker’s powdered gelatine or the same 12 sheets of the leaf gelatine.

By the way, I tried to calculate the calorie count – each of the 12 portions is about 295kcal.

Mine tasted good, but looked a bit insipid – I can’t wait to try it again, taking my own advice …

You need to microwave the unflavored gelatin to melt it, so it will be easier to combine with the milk mixture.

Hi Penny, thank you for pointing that out. I am not familiar with that brand of gelatin. Also, this recipe was just updated and somehow the notes before were deleted but I added them again. You will need enough gelatin to set about 5 cups of milk mixture, so the quantity may vary depending on the brand you use, but the it will be easier to follow the instructions if you know how much liquid you need to set.