Here is the diet which seems to be working very well for me.
Brekfast - oatbran porridge with whole milk - NB must be oatbran and definitely not wheat. oatbran contains more soluble fibre
mid morning - large bowl fruit salad and full fat yoghurt
lunch - small piece of white meat or white fish, some vegetables and some quinoa. (quinoa like oats contains soluble fibre)
evening - small oatbran porridge and small fruit salad.
i eat this every day at the moment. its not very exciting, but fissure seems to be healing consistently which is pretty much all i care about these days!
the key point (i think) is to get a good balance of soluble and insoluble fibre. for me this meant not eating any wheat (bread, wheat based meuslis, porridge, bran etc - all mostly insoluble fibre) and eating more oatbran in place of wheat and quinoa in place of brown rice. most fruit and veg seem to contain both soluble and insoluble fibre and i find i can pretty much eat whatever fruit or veg i want.
i have also read a lot about wheat and gluten intolerance being possilbly related to fissures. I don't think this is the case for me, but it is another good reason to cut them out.