Lots of people on our allotment site have flags; it started about six years ago when one of our plot holders returned from visiting his daughter in Australia and hoisted an Australian flag. One of the householders who overlooks the allotments complained to the Council about having a flag flying but the Council told them there was no rule against flying a flag on the allotments . . . . . so it was followed by a lot more! After all they're 'bird scarers' to keep the pigeons off the brassicas, aren't they! Some of our plot holders have made their own flags - a white background with their plot number on which is probably quite a good idea. My current flag, the Union flag, is getting a bit tatty so I'll be replacing it soon.