Chickensniffer, I think it's great that you're trying to get a better idea of the factors affecting the types of approaches that helicopters do. It's a lot better than what a lot of people seem to do - complain strongly in the first instance and in so doing immediately kill any chance of a meaningful dialogue between themselves and the helicopter operator.
The videos of the helicopter approaches that you've put up show normal and benign activities, and certainly don't seem to be indicating any directed attempts to do anything that might adversely affect your horses. From what you've said of the response from the company after the first approach, they've taken quick and appropriate action as evidenced by the normal-looking approaches on the videos you've put up.
Helicopters will often circle a landing area to assess the wind (which they should almost always land into, or close to) or to check the landing area for obstacles, loose items, wires etc, so if you see a helicopter doing that, it would be my first guess as to what it was up to.
That first approach may even have been someone initially mis-identifying the landing point, and realising when on approach that it wasn't the exact right spot (i.e. a horse paddock rather than a clear landing area!), and aborting the landing, leading to a lower-than-normal overflight of your place.
Regarding putting in a clear request not to fly over your place for a good reason (not scaring the stock), you certainly can do that as Hueyracer said - any decent helicopter operator would inform their pilots of the issue and brief them to avoid your place by as large a margin as is practicable and safe.
Helicopters need to be able to operate without undue restriction and landowners need to be able to protect their interests with respect to noise and stock, but if everyone is adult and reasonable about it, the two can co-exist happily. If the helicopter operator doesn't do the right thing or the property owner takes the tack that the very sight or sound of a helicopter is a personal attack, that's when things get out of hand.
Horses and cattle get used to helicopters pretty quickly too, and now the company knows where you are and that you have horses, it would seem unlikely there'd be further problems. Helicopters sometimes get a bad rap because they're something out of the ordinary, but with all the motorbikes, trucks, chainsaws etc around the place they are just another factor in the overall picture.