It will take a long long time to go to court if the EH have evidence. Two warnings are issued first with independant evidence from sound equipment.
Whilst you say they are not noisy, be real. A woman on her own compared with 4 students and no doubt countless visitors!!!!. They perhaps do not realise the noise they make. It does not take a Roman Orgy to annoy the neighbors.
A lot of noise travels through the walls as opposed to the common belief, the floorboards. How about asking the landlord to cavity fill the walls? It only takes a few hours and he may receive a grant from the council if they are Green orientated.
Also, turn the bass off any stereos and the TV and place slam stops on all doors.
Remember, the complainee may work shifts and/or weekends, so Friday night revelries may be annoying.
Whilst I am no grouch (I was a student once!!) I do feel for the woman as well. I lived in a flat once for two weeks and the noise was horrendous.