Complaints of this nature will occasionally be received by local authorities. Clearly, the time of day increases the likelihood for such activity to be more intrusive; as this tends to be more of a late night activity any screaming, moaning, wall banging or other associated noise can easily interfere with sleep.
If your neighbour is particularly noisy in their activities you might want to say something to let them know that it is waking you up. A well-timed hint or comment (for example, relating to the level of sound-proofing) might be enough. However, you may have to be a bit more direct though if the problem persists. If you do approach the neighbour remember to be discreet and try to minimise the chances of embarrassment. Sometimes neighbours don’t realise that they may only be a few feet away from each other when lying in their own beds. From a practical point of view, and in the short-term, changing the position of beds (away from the adjoining wall) may help in some circumstances.
Where the problem is very regular or unusually loud (and where the informal approach is unsuccessful) statutory nuisance powers could be used. However, the anti-social behaviour legislation may be more appropriate. There may be issues concerned with privacy where sound recording equipment is concerned and so establishing a body of evidence may be difficult.
Where there are frequent visitors to property and you suspect that activities taking place form part of a wider, more organised, undertaking the anti-social behaviour powers also provide some useful enforcement mechanisms. One of those mechanisms enables the local authority to close the building and prevent access to those who do not reside at the property.