Ours is driving me nuts... We would like a reasonably big one so we don't have to empty it constantly (it's a bit of a pain getting at our compost heap especially when it's dark or wet), and we have got the green Lakeland 9-litre one , which we use with compostable bags so it doesn't go too manky and need washing every time (especially given we are trying to empty it less often).
But every bag I've tried, including their own brand and others, is too short and either doesn't reach to the top and has a gap where things fall down and go yucky (esp. the paper ones), or they do reach to the top but barely go over the edge, so as soon as we start putting things in they collapse down and again stuff starts going down the outside of the bag (or it all just falls in and the peelings end up on top).
Please please, if you have found a container with bags that actually fit it which isn't too teeny, or if you have found some bags that really work with the Lakeland one, let me know so I don't end up swearing at a slimy/mouldy caddy all the time!