You can buy any land you want. A lot of people buy a bare plot of land up here off local farmers etc. and build a house. You have to get planning permission to build. 1 acre of land, depending where it is with outline planning permission for a house can cost quite a bit.
Here is an example.

Roadside Plot, Barrock
Offers Over £35000

Set in an idyllic country location this large plot extends to approximately 100m x 80m with additional land available by separate negotiation. There are panoramic views across the open countryside. It has outline planning permission for the erection of a dwellinghouse and garage. There is mains water, electricity and telephone nearby. It will be the purchaser’s responsibility to install a private drainage system.

A plot in one of the towns, Thurso or Wick can cost up to £80000

Chris.