You need to call your Environmental Health Department at the Local Council and start noise monitoring. If you can prove the noise is loud and persistent enough to be causing you a nuisance they can take action as a Statutory Noise nuisance. It has to be disturbing your life somehow rather than just being annoying - stopping you sleep, for example. Good luck.
It's a tricky one because they are conceivable acting within the bounds of the licence - in this case, music up to 3:00 a.m.
Your Environmental Health Department will come and investigate, and if they deem it necessary, they will install equipment that will measure the noise levels at your property, and if they contravene accepted legal limits (which may not be the same as your perceived limits, so be aware of that) they will enforce a noise reduction order.
It's selfish, isn't it when neighbours are noisy at unearthly times of the night. We have a neighbour with a diesel van who generally sits with it running for 2 to 3 minutes in the mornings before pulling off - this is at 5.30! The other morning he sat there for 26 minutes with shouting in between the ticking over of the engine. Unbelievably selfish and uncalled for IMO.
I dont have a solution to your problem I'm afraid but I do commiserate with you
Obtainn a copy of their license from the Council. Even if they have a license til 3 there is often a clause that states the noise and vibrations shouldn't be audible to neighbours so as to cause a nuisance.
They won't know for sure that their noise is bothering you until you tell them.
You could write and ask them if they could do anything about it.
There are ways.
I think Albags is right, a letter to them in the first instance asking if they could do something about this, in the event they cant or wont then it may be a case for the environmental health team to look at.
oj I have similar, 5.15 in the morning but with motorcycle and he has it on choke (full revs) for at least 5 minutes and then roars away with a very noisy engine. In the summer with window open it is a curse but I daren't say or do anything just in case there is any retaliation, you never know nowadays do you.
A few years ago we had a neighbour who used to leave home on his moped at 6.30 each morning. His garage was in a block at the side of our house and as he left and went past our house, then his own house, he used to 'beep-beep' to his wife - until one night he left his moped outside his garage and MOH cut the cable to his 'beep-beep'!!