Whether ghosts exist or not is not really relevant to the turn this discussion has taken.
Now one of the dwellers in the house in question has been made uncomfortalbe by "noises in the night".
In your place OP I would suggest she/he checks all the mundane things that could cause this - a branch of a tree or bush brushing against a window, a draught causing and inside door to blow shut or open, a bubble of air in the central heating system or faulty plumbing, a bird trapped in a chimney or attic if the house has either of these features, rats (just as scary as ghosts and unlike ghosts definitely known to exist.) Or an ancient fridge that needs replacing making odd noises.
I have known most of this list to be the cause of "things that go bump in the night", If none of these suggestions proves to be the cause, then the person who has heard the sounds will either conclude that the house is haunted or that she/he imagined the sounds or dreamed them.
If that person believes the house to be haunted, you can suggest the options listed in these answers for getting rid of ghosts - they presumably work, whether or not one actually believes in ghosts, if one has convinced oneself that that is what one is dealing with.
I have been considerably surprised to learn that in the UK one is supposed to declare any violent happenings that occured in a house. When did this become customary?
A couple of years ago, the person who bought my childhood home from my parents in 1980 contacted me to ask if it was true that a friend of my parents' had died in the house while we lived there.
I told him it was not, but suggested that rumours of a death in the house, that had been built in 1860, might be attributed to the fact that my parents bought the house from the estate of a deceased owner, that my grandmother's funeral took place from the house and her coffin had stood in our sitting-room, or from the fact that my parents before moving to the house in 1951 had lost a new-born premature son in a completely different part of Britain.
Any house older than around 1980 will have witnessed births and deaths, so to me it is sheer nonsense to expect house owners to know about all of these and be able to list them,
I once lived in a flat that was haunted (I am not kidding, people I had never told of the ghost saw it as well as I) by a little black cat - the sweetest apparition you could ever hope to meet and no, I did not tell the family I sold that flat to about that cat, as I did not want them to think I was crazy.