Re: Where's me 12-bore?
From a practical point of view, you would have to ensure that none of the shot falls outside of your own property. For anyone in the suburbs, that will be difficult. Given a sufficiently pastoral setting, this is not a problem.
However, even with a 32" barrelled trap gun with full chokes (I shoot a 32" Gold E Xtrap), you are not going to be hitting much beyond 60-80 yards - and that is both in horizontal and vertical distance. I know highly skilled clay competitors like George Digweed can hit out to 100+ yards, but frankly, that isn't you, and your likely gun and chokes. And after they operator hears the first shot, he will send that drone straight up at full throttle, if he has any sense. So you have one or two shots at most, likely at a target just at or beyond your maximum range.
The real issue is that it is likely that the drone will have a camera, and will quite possibly have you on video as firing at it, and.or destroying it. That is destruction of property, and unless you can prove the drone was a threat to you, you will likely be done for that. I don't think it will be a firearms offence per se - but with the plod trying to do it's utmost to limit ownership, being convicted of the destruction of property may very well be enough for them to pull your Section 2 Shotgun license, and certainly your Section 1 Firearms license if you have one. These are being pulled for convictions such as even getting into a physical fight in self-defence, or too many speeding tickets, or a single drink driving conviction, to put that in perspective. Wanton destruction of other's property is pretty close to that sort of thing, and at that point I believe you would be at the mercy of whatever judgement your local firearms team would happen to make. Some may laugh it off, some may put you under caution, some may revoke or suspend. You can challenge any action in court of course, at your own expense. In my mind, it isn't worth the risk, given how hard they are to get back.