I think your idea of fresh fruit is great.
I have started just cutting up fresh fruit in the evenings and popping it in tupperware (well those that don't go brown) we all really love pineapples in our family and a whole one makes a nice big tub (plus it's a super speed superfree food on SW) I sometimes put a bit of zero fat yoghurt on it then it's just like a desert.
Just looking at UK supermarkets seems Asda do a whole pineapple for 75p which would probably do you a few snacks and I am sure other fruits would be similarly cost effective. The pre done tubs can be really expensive so it's worth the bit of faff doing a few yourself at once.
Our pineapples we got here recently in Denmark were about £1.80 but as I said to husband, we're saving on not eating junk, we now just drink water and tea, no soft drinks, wine or beers, no trips to the bakery. So it's now our treat to ourselves
Best of luck!