But why buy?
We use a yoghurt maker (from Lakeland - about £19 ) It's extremely simple to make. You just pour in a litre of full-cream UHT milk and a spoonful of starter yog, leave it overnight and it's ready to eat once it's cooled down. The quality is great, and the cost is about 45p a litre. You can also make a (sort of) greek style by adding cream.
One great advantage is that you know exactly what goes into it. With supermarket stuff you don't.
David Wilson