Self-build and custom housebuilding

According to the Housing and Planning Act 2016:

'Self-build and custom housebuilding' means the building or completion by - 

(a) individuals
(b) associations of individuals, or
(c) persons working with or for individuals or associations of individuals,

of houses to be occupied as homes by those individuals.

But it does not include the building of a house on a plot acquired from a person who builds the house wholly or mainly to plans or specifications decided or offered by that person.