i'm not sure if this is the right place to put this but i didnt no were else to put it, does anyone know were i can find out how much P&P would be for some fish items??
Do you have some kitchen scales ? That might help.
Failing that (if you don't have any), I used to get some stuff in the kitchen (like a block of butter or a bag of sugar) that I knew the exact weight of, and roughly tried to judge that way. Hold packaged item in one hand and block of butter in other, and have a guess
Obviously that will be a rough indication only and very much dependant on how well you judge weight from one hand to the other.