Is it easy to get planning permission for a garden office in the front garden?

Apologies if this post isn't allowed. Read the rules and think it is.

I'm currently house hunting, with a low budget, but one thing I really want is a garden office/music room. A lot of places in my budget in the areas I'm looking at have a large fenced garden at the front of the property.

My understanding is that this is outside permitted planning, so I would need planning permission. How hard is it to get permission for buildings in the front garden?

Fyi I'm in the south east, if that clarified anything.