It seems entirely random. On this site the current permission is for something that looks like the house next door, we don't particularly like it. Yet across the road when a house was built in another listed house garden they insisted on something modern and not a "pastiche".
The funny thing is that after years of argument, they approved a modern house across the road. Someone then bought the land and reapplied for a much less interesting, cheaper to build house and it just sailed through with no argument.
I am still suspicious that in fact the planner was going to approve our house and his boss stopped him.
In the immediate vicinity of 7 or 8 houses, there is a render and brick listed house, a sandstone listed house, two rendered 1930s houses, a render and zinc 2015 house, a red brick 1980s house a render and stone 1980s house and a pebbledash 1970s house.