Wall vs. Fence

Hi there,
I have spent a while looking on google and this forum but I still require some help please.
I am in the process of buying a site and the seller ( who is a farmer ) is insisting that I build a wall straight away around the perimeter of the site – nearly an acre.

I think a concrete wall will look terrible in nice countryside and will also cost a fortune.
He says that it is the only way to guarantee that his sheep and cows cannot get into the site. I can understand his concern for the animals, but if that was the case then the country would be filled with concrete walls and I can’t see any.

I have researched it and it seems that you don’t need planning permission for a wall if it is under a certain height – 2 metres at the back and rear and 1.2m at the front. But does this relate to an existing dwelling or can it just be a field.

The county council said that would prefer a fence but there does not seem to be a definite rule on this.

Any help appreciated.