Good plan!
Might also be worth gathering info on the councils that don't have a problem - there must be loads of people on this forum that either do or could keep chickens on their allotments. I know in Sheffield you can keep 6 hens, or 2 ducks, or something else (I think it might be goats but don't quote me!).
Mind you, you can't get an allotment in the first place :roll: