Depending on how good your self control is I think WW cakes and icecreams or skinny cow ice creams are really good for being low in cals and getting the sweetness. I personally don't buy WW cakes/biscuits or sweet things or anything like that because I'm awful with self control. As soon as I have one of something I just want to eat the rest of the packet. I don't do moderation! once I've had the taste I go in to feeding frenzy mode

so I try to avoid anything that tastes chocolatey like the plague otherwise they'd only last an hour. I feel like I may aswell just avoid stuff like that altogether since I dont see the point in just eating one

say if I had one penguin bar at 107cals or a kitkat bar at the same amount I wouldnt feel satisfied afterwards I'd just want more. So I don't bother now! *greedy*
So when I get hungry after tea and I want something sweet I make little fruit cups. You can have bigger portions of healthier stuff for a similar amount of calories and less fat anyway.
Usually few strawbs, blueberries, sliced apple, some 0%fat yogurt or low calorie and fat yogurt, few raisins and a bit of dried banana. I sometimes have it with sugar free jelly instead of yogurt. Like someone mentioned here, hartleys do little pots of sugar free jelly that range from about 8-10cals and they're really nice.
Also find that dried banana is really sweet(but high in calories, so don't eat too many!) I only have a few slices per time. About 4-5 slices of dried banana with 3-4 cashew nuts. They go nice together but I doubt this would fill you up but it really helps me when it comes to the sweetness.
I've also recently started to freeze mullerlight yogurts for a few hours and they taste really nice, a bit like ice cream.
I don't do this very often, as it's still higher in cals than I'd usually like now a days but when I was preg I had gestational diabetes, and I couldnt eat any chocolate or anything high in sugar so I started making low cal, low sugar triffles.
Light/low fat double cream whipped
No added sugar/ low fat custard sachets
Sugar free jelly and add some fruit or something! they come in quite low in cals if you measure everything out right. Only about 8-10cals for the jelly then about 100cals for the custard and cream, if you only have a small portion of them. I make my triffles in little pots. I think I'm going to make one tomorrow actually
x