I am selling my holding and was approached by a neighbour wanting about half an acre directly adjacent to their house which would turn a 2 car parking area that has to be reversed into off the road into a turning circle and parking for a motorhome plus a back garden outside their back door rather than livestock. Agent I am with said the value to an adjoining house would be £10-20k/acre for both amenity enjoyment and increased value of the house. They offered £2.5k as agricultural value. I politely declined because it isn't worth the hassle for less than £10k minimum - legal fees and all the paperwork, paying for formal markers and refencing even with shared costs.
I would say if you want the land you only have one chance. If you wake up tomorrow and find someone coming and going twice a day to check on 2 small ponies or half a dozen sheep, goats, alpacas or a large flock of hens and cockerels crowing, how do you feel? If you want control of the proximity you pay for that. If it increased your valuation, better still but it makes it more saleable either way. Privacy matters more to me than most and I'd hate a 2 acre non resident livestock owner coming in and out. They might sell to a dog club/dogwalking field with lots of yapping day and night and agility competitions every weekend. Or a desperate horsey person WILL pay that for their 1 horse and a shetland companion if they can't get anywhere else. Livery costs add up to more than loan repayments so don't assume everyone will put the value where you do or the large scale farmers to whom it's just any old acre not your immediate neighbour to come for years ahead..