Last bit first:
Anyone who is on their own property or on public land (or where they have permission from the landowner) is free to watch and (if they so choose) photograph or film anything or anyone within their view, irrespective of the location of the the objects or people they might be viewing. (For example, it's perfectly lawful to stand in the street and film people in their front gardens or in their front rooms). There are a few limited exceptions to that statement (covering, for example, 'official secrets', 'voyeurism' and 'indecent images of children', but none of them seem to be relevant here).
Unless there are relevant covenants prohibiting it, you can normally store a single unoccupied caravan on your land without the need for planning permission. However making use of that caravan, while it's on your land, for any purpose (e.g. as an office or as accommodation) would normally be regarded as a 'change of use' for the land which it stands on, requiring planning permission.
There's an exception to the requirement for planning permission when a single caravan is parked within the grounds of a house and is used solely 'in a manner which is ancillary to the main property'. i.e. it can normally be used as an annex to the house without planning permission but it can't be used as a separate residence. It's not completely clear from your post whether the caravan is parked within the grounds of your house, or elsewhere. If it's with your house then you may not need planning permission; if it's elsewhere you almost certainly do.
Chris