UPDATE:
Well, we're still calling the rozzers out at a minimum regularity of once a week, and our neighbours have now added loud shagging to their growing list of noise crimes. I suppose it makes a change from listening to them beat the crap out of one another whilst listening to techno, but certainly no the more pleasant for it.
So I'm wondering, how many times do you have to call the police out before they will actually take more serious action? They are wasting a vast amount of time in banging on my neighbours' door and I would have thought that they'd be as bored as I am of my 3am phone calls, and be on to stage 2 of the 'shutting people up' plan? What powers do the police have in this situation? Does it take a court order? I've tried asking them myself on the phone, but got a very vague ‘we are monitoring the situation' response.
I guess now would be the time to bring out the big guns and have a baby, as I really can't be any more sleep deprived and the screaming might drown out the hideous noises...