Thanks for all the replies.
My 2 (7 and 4) are offered fruit after each meal, both of them love fruit so they almost always have some. The little one doesn't like yogurt, the older one only likes plain natural yogurt so sometimes has that for breakfast not as pudding. After their fruit they can choose 1 thing from their 'treat box' if there's anything in it (this will be chocolate/sweets etc from party bags, Christmas, Halloween, Easter etc depending on season!) only allowed 1 thing (older one occasionally has 2) and so it's very little, e.g. last night it was a tiny choc football for DS and a mini choc coin for DD. If there's nothing in their box for whatever reason I don't specifically buy stuff for it, so wouldn't go to supermarket and buy 'treat' stuff.
Sometimes, especially if they have a friend over, I'll buy mini ice creams on sticks (think like a mini magnum but supermarket own cheaper version) and the can have those. DS will only take a couple of bites and then leave it so I encourage him not to bother and generally he isn't fussed. There's no 'rule' about having to eat all your main course to get pudding but if they haven't made a decent attempt at it there's nothing else.
DD does a lot of sport and sometimes (but no way every time because it would be too often!) I'll let her chose something out of the vending machine at the leisure Centre/gym after her training but she's quite sensible and will rarely eat the whole thing- e.g. The other day she chose a Twix and ate one stick and saved the other for another day.
I like baking and the kids do too, so perhaps once every 2 weeks we will bake and they will have whatever we bake for pudding after dinner. Little one has been watching I can cook and wants to make marmalade cake so we're doing that on Monday!
At school (both there every day for lunch and have school lunches) they are offered 'pudding' every day, but once a week it's only fruit, once a week it's cheese and crackers, so only x 3 a week is it a 'proper' pudding and neither of them much like the puddings so have none or choose the fruit. I'd guess they only have a school pudding max once a week if it's something like ice cream/