I use the Green's mixes. I had some issues with them not cooking in the middle and found that the American mixes are commonly 517g, while the Green's is 470g, and that seems to be what was causing the problem. So you need to buy more than 1 mix, and weigh out the correct amount.
Cakelass - Cottees put out an Instant Pudding Mix.
Either chocolate - strawberry or vanilla.
I was given a Red Velvet Cake Recipe on here from GrandmaG and it calls for a Packet Yellow Cake (i will use the Greens Buttercake Mix) and a Packet of the Chocolate Instant Pudding Mix.
Will try and load an attachment to show you the packet of pudding mix i am talking about.
Its found in all Supermarkets - in the Dessert Isle....Near the Self Saucing Puddings.
As scgriffiths said - the Packets in the USA vary alot from our size of packaging.
And remember -
Australian Tablespoons = 20ml
whereas the
USA Tablespoons = 15ml -
and so on.... when converting liquid measurements.
Hope this helps you
Bluehue. 
Thankyou for your replies.
I had sen the pudding mix but wasn't sure if it was the same.
Also thanks for the weight of cake mixes.
I feel so frustrated when you read all the wonderful ideas on the site and cannot try them.
While on the subject of substitution has anyone tried bettercreme or a substitute.?
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