It's easy to get overwhelmed by all the foods out there, but the most important thing is to feed a complete food. There are a lot of complementary foods out there (a lot of those described as "gourmet" are complementary so should only be fed occasionally and shouldn't make up more than 10% of the diet. Provided you feed a complete food, your cat will be fine. To begin with, you should feed your cat whatever she is used to eating and make any changes slowly. If she has just had kittens and needs feeding up, kitten food might be a good idea to begin with.
Objectively, foods with a high meat content are better for a cat than those with a low meat content and lots of cereals, but if she will only eat felix, whiskas etc. she will still do fine. If she is fine with the higher meat stuff, try hi life essentials (available from morrisons), tesco finest and tesco luxury, pets at home Purely, Tesco just nature and Morrisons The Best. I also feed animonda, bozita, schmusy and a few others that I buy online from zooplus. Aopplaws and almo nature usually go down well but they are complementary foods.
Wet food is good for the water content but if you want to feed some dry alongside, that can be convenient (I wouldn'nt persoanally recommend feeding all dry unless that's all she will eat). As far as dry food goes, applaws (available from PAH) and Orijen (available from zooplus and a few other online suppliers but not in shops as far as I know) are both grain free dry foods with approx 80% meat. Alternatively, pretty decent dry foods include PAH premium (in the silver bag), PAH Purely, James Wellbeloved, hi life, Joe and Jills etc. Best to avoid the supermarket dries such as go cat and whiskas if possible.