I'd just add that I ferment my yogurt in a fan oven set for 45C, and it's done in about 10 hours. I use the Yeo Valley stuff as a starter.
When I make Greek yogurt, if it's too sharp, I fold in no more than 25% whipped cream.
And the cheese I made was just yogurt made from organic milk strained as per Greek style, and then some more. I stirred in about 1% salt when it was nice and thick, then pressed it under a 2kg weight until it stopped dripping, formed it into a log in foil twisted in a tea-towel, then rolled the log in cracked black pepper. It WAS very good