What's the best cat food in Uk for helping increase weight?

Well some of my friends will hate me for this because they look at Whiskas as the cat version of McDonalds but I've had (still have one) three tom cats who've been brought up on the stuff and they all peaked at around 7Kg by the time they were 4 or 5. My current moggy (he's 12 next month) prefers the Whiskas jelly but is happy to scoff the Supermeat. He goes through a can a day and although he's big he's not obese. He has the occasional treat maybe once or twice a week (bit of uncooked bacon, cooked chicken or his favourite a cheese and onion crisp or three).