Does the owner of the land without the CPH want to have one or even know it's an option for them to just phone and get one? They should have first right to decide since it's free and there are benefits to a landowner to having one eg if they want to rent to other livestock owners in future or want to sell up at some stage and market as a smallholding. There is also for me simply the feeling of 'owning a holding' which I remember well when I transferred my land to my CPH both times, the first being simply a special moment of achievement of a dream. Which that owner might not have, but still, their land, their choice.
If there are no other agri livestock on the holdings concerned then movement standstills don't matter to anyone but you anyway.
And if the holdings are a few miles apart then I would imagine (though I admit I don't know) that you would still need to register the movement in some way as you are taking potential disease from place A to place B even if you 'hold' both on your paperwork. In that neighbouring farms' livestock in adjacent holdings will be within transmission range because of your movements, where they would otherwise not be. As I say I don't know, but it would make sense to register the flock as yours and the two or more blocks of land are held by the landowner with the relevant CPHs. OK it makes for paperwork for you but a. you may have it anyway and b. it is the system which best prevents/tracks disease.
Otherwise why call the CPH a Holding number rather than a 'livestock holder' number? It's land registered not people or animals, which is why the flocks/herds etc have separate systems..
Oh and if the holding with the CPH has one section removed and re-registered as 'your CPH holding' or part of it, that affects the landowner's use and decision making on their own land in terms of wanting to shift your sheep elsewhere for convenience or as a favour, crossing between their own and 'your' CPH for any reason etc - unless you have totally separate access that doesn't cross or use any facility of that CPH other than the one you've reregistered.. If you do, then standstill and any disease containment measures taken by government order would still apply anyway.