The house next to my aunt has been empty for 17 years. The lady who lived there died, and since its been left to the elements. Its condition is deteriating and it may affect my aunts house. It has a huge garden and i was wondering if there is any way i can claim onwership of the house? How would i do this?
Unless it is attached to it, it is unlikely to impact your aunt's house.
To claim ownership of the land (and its house) you need to occupy it and maintain it for at least 10 years before you can even start to contemplate making a claim for adverse possession. It's a long term project, and you might be turfed out by the legal owner during that period.