Often, grooming caused by an allergic reaction to food happens right after eating. Environmental factors may also cause allergies. Note changes in the environment like the presence of flies, plants, insects, the weather, etc.
Infectious skin diseases can also cause itchiness in cats which trigger the natural response of grooming. Cats who stay indoors are less likely to encounter skin complications but if you suspect this to be the case, let your veterinarian know so that skin testing procedures can be performed.
Your vet will help you in determining exactly what’s causing your cat to groom too much and once all medical reasons have been ruled out, then it could be that it’s a behavioral problem that’s causing the cat to over-groom. The cat may be under too much stress because you either moved to a new house, or there are new people or cats nearby, etc. It could also be that your cat is just bored and in that case, a cat scratching post may help distract your cat from excessive grooming. You can find one from a pet shop in West Wickham called Waggles Pet Emporium.