Please don't feed Purina and other supermarket foods. These foods are full of sugar, fillers and very poor quality ingredients. They can barely be classed as food. I'm a cat carer and the cats I visit which are fed these foods are lethargic and sluggish with poor coats. I'm clearing up vomit sometimes at every visit. Contrary to popular opinion, it is not normal for a cat to vomit every day. People will endlessly justify why they feed them, but it's not difficult to transfer them onto proper nutritionally balanced foods, I know because I've done it. You wouldn't feed your kids McDonald's for every meal, so why do it to a pet? Apart from my allergic cat which is on hydrolysed protein, my other two cats (11 and 5) have never vomited in their lives. No diarrhoea either. You can claim that your cats are healthy, but you can't see inside them. Cats are also adept at hiding pain and illness so you won't necessarily know if they're feeling sick or experiencing pain.
Problems associated with poor quality foods include gastrointestinal discomfort and intolerances - vomiting and diarrhea.
Sugar leading to obesity, diabetes, arthritis and tooth decay.
Generalised poor condition which can leave the cat susceptible to other diseases and infections.
And the big problem of pancreatitis which is intensely painful and a cause of death if a cat is fed inflammatory causing foods for too long. Cats are not designed to eat sugars, cereals and other fillers.
People can get away with feeding poor quality foods for so long, but it will catch up with them as they age and have increasing problems digesting and processing these products. It is not a kindness to allow your cat to dictate to you what it will eat. They can be transferred into proper food with some time and patience and trying different high quality products. Kittens are even easier to transfer.
If all you can afford is cheaper foods, then at least don't feed Whiskers, Go Cat, Felix and Sheba. Buy Sainsbury's own brand fish or something like Encore. These are intermediate quality foods and probably won't cause harm at least.
Zooplus have a good selection of foods. Look for higher protein and fewer fillers and sugar.