Buying property- existing garage is not within PD

Evening all,

I'm buying a house which has a detached brick garage to the rear. It is right on the boundary to next door, next to their garage. The roof is a mono pitch and is at its maximum height on the neighbour's side. It's really high. It looks to be closer to 4m than 3m.

I can't find any evidence of planning being sought on the council planning portal and it obviously isn't within PD.

The garage was built in 1999.

Presumably if someone were to take exception to it I could be forced to take it down?

What would you do in my situation?