lol at the cat being smarter than the kitten - Willow is a lovely lovely cat, but um, no, not the sharpest crayon in the box
She's actually currently eating again, so that's fixed it just now, but she probably won't be again in a few days. :(
Clingfilm would keep Flump out of her food, but that works the same as the fridge, I'd have to keep giving it back to her. I can do different rooms, but it means shutting one of them in or out of somewhere, which seems cruel, I was hoping maybe there was a dead easy solution that I'd missed, lol
It's not that she's not around it's that she just wasn't eating it, so then Flump was getting it and then Willow would come back looking like maybe she did want some now, so desperate to feed her up I was trying again - with the same result, rofl.
Flump was ecstatic at this though to be fair, every-time she appeared in the kitchen there was nice food there for her, I swear she put on weight by the hour, lol.
I quite like your worktop solution ormirian - in theory my cats aren't allowed up there, but what actually happens is that they don't go up there if they think I'm watching, if I'm looking away or in another room they seen to think they're fair game 
so I've just resigned myself to assuming that there has been a cat up there and to clean accordingly before I use them.
I need somewhere Willow can get that Flump can't, but as I've yet to find anywhere that she doesn't get into...the only way the toilet roll is safe is to keep it on a shelf with the bathroom door shut and she's still managing to make confetti, rofl (of course it doesn't help that my children don't seem to understand the concept of shutting doors)