Hi everyone

I was wondering if anyone knew of any ways to improve your rhythm? Perhaps any exercises, or ideal pieces?
I can play a few fairly technically demanding pieces, but my rhythm sucks. For example, I could learn one of Beethoven's easier sonatas (bottom 10), no problem if the rhythm isn't too demandubg. Yet I struggle with Mozart's Sonata K545 (only looked at first movement), simply because of the rhythm.
At the moment I try and learn a piece slow enough for me to count the beats without too much trouble, find the correct metronome marking for that slow speed, and then gradually speed it up. As soon as the metronomes gone though, I begin to make mistakes with the rhythm. I tried just speeding up without a metronome, but I end up speeding up too rapidly, from say 70bpm to 100bpm.
So I'm looking for any pieces that aren't technically demanding (around Mozarts K545 sonata), yet would be good to improve my rhythm. Or perhaps if any composers like czerny or hanon etc did exercises specific for rhythm, or if you know of any exercises?
Thanks for your time, it'll be a great help!
Evan.