Hello! Long time no speak, and then I come wanting advice, sorry

Geoffrey just gets fatter and fatter, and it's now getting serious...he's up to 7.7kg which is the biggest he's ever been - we know he's a big cat but at 7kg he was already overweight. For the past few months I've been trying them on a raw food diet (natural instinct) to see if that helps with Milly's skin problems and Geoffrey's weight, as I'd heard that often it is the carb which causes the weight gain and the raw food diet is just pure protein. But in that time he's put on over half a kilo so I'm guessing not...
So, back to the drawing board. I guess I could stick with the raw food but drop the quantities, although I'm not sure that would make for a happy boy as he isn't getting much as it is. Or I could revert back to one of the multitude of diet foods out there. The question is, which one!! I've been through them all at some point in the past but I've lost track of what's good/bad/indifferent. He did ok on the Royal Canin obesity control before, but I hear a lot of concern about the quality of RC foods, especially given the price. Is there anything that anyone can recommend? I've had a look on zooplus and there are a few foods there I've never heard of (integra protect, kattovit, perfect fit)...anyone know anything about any of those??
Geoffrey has never been free fed and they have been on raw only but there is still some food in the cupboard, and my OH has got into bad habits of giving him a handful of biscuits (arden grange light) whenever he miaows at him, so I've told him this has to stop and that Geoffrey must only have his 2 meals and nothing else. He just can't seem to get his head around the fact that the cat food is in the fridge!!
All suggestions gratefully received...