My friends neighbour has built a sheltered cover from the extension into the garden using wooden posts, its about 15ft into the garden and is above the height of the fence. The roof is plastic. Is this allowed?
I don't kno the legal requirement but i'm pretty sure if it's as high as 15ft it would need planning permission. You can ask your council what height a construction needs to be before it requires planning permission - you don't have to give your neighbours details or anything and just say it is a general enquiry.
If it is over the permitted height you can then decide whether to report it or not.
hope this is of some help
Also if it does need planning permission, you will be able to object to it if you feel it interfers with your quality of living. If council do not consent to it, it will have to be taken down even if it has already been built.