There are a few good 'sensitive' diets, but I did notice that Whites Premium have a new one out (Light and Sensitive) which is based on Salmon and Rice and looks to fit the bill. (check it out on www.pet-pantry.co.uk)

The main thing if you have an episode of digestive upset is not to suddenly switch foods. It's best to just feed a little chicken and cooked rice (or fish) for a few days to give the system a rest, and then gradually introduce the pet food back into the diet.