> "Ugly" is not part of planning regs.

The phrase "materially affect the appearance of the building" has a pretty strong implication that the aesthetic effect is regarded as undesirable.

> Yes, those are things like "it's too big" or "it's a listed building."

And what then happens in the cases where "it's too big" or "it's a listed building"?

It also includes things like "it's going on a pitched roof" or "it's too close to the property line".

> show these cases that are obviously reasonable but still being blocked.

Demanding "obviously reasonable" is the crux of the banality of evil. Many things are non-obviously reasonable.

Who needs to put the unit on a pitched roof? That's weird. Just put it on the ground. Unless you own a unit on the second floor of a building and someone else owns the yard, and then you can't.

Your link has "too close to the property line" at within a meter. That's really close, who would need to do that? Well, the UK has millions of terraced houses that directly abut the property line. Some of them don't have a yard at all (and then we're back to the roof), others have one so small that being that close to the property line may be the only available place to put it.

Are these cases "obviously reasonable"? Putting the unit on a pitched roof is still weird and ugly. It's not that hard to understand the neighbors not wanting it that close to the property line.

But there is nowhere else to put it and then July makes the building hot enough to be a danger to life. At which point a rule motivated by the aesthetics is doing something objectionable.