Contact the BBKA, who I know to support beekeeping on allotments. Try to find others who keep bees on allotments, and see if you can get a campaign started. The main problem is ignorance; if you keep good-tempered, low-swarming bees in reasonable numbers, and have them behind a six-foot fence or hedge so they they fly above head level, there's no need for them to bother anyone. I've had bees on my plot, illegally, for five years, and never had a problem. There's absolutely no need for beekeeping to have a poor image, especially given the importance of bees to the economy (about 1/3 of our food supply depends, directly or indirectly, on pollination by bees).
