They may be too drunk to realise the consequences
So make sure they know the consequences before getting drunk. If they know they are going to be severely punished they won't do the crime. Look how rare heckling at Labour party conferences or upsetting the Welsh on TV is becoming.
AIUI you are more likely to be locked up for not paying your council tax than beating someone senseless. £150 fine for assualting a Police officer, thats hardly going to deter a drunken reveller make it a month's wages or Benefits.
If you can't lock them up then get them up at 5 am to clean the puke from the streets or even better pop them in the cells for a night (you have to make sure they don't drown in their own vomit or die from their wounds) and after a cold shower in the morning give them overalls so they can do it with a hangover. They can go home in their disposable overalls so everyone can see they have slept it off in the cells. Obviously charge them for the overalls & accomodation, benefit witholding & credit cards accepted.
If they don't turn up for cleaning duty pop round and arrest them at work, or stop their benefits.
Make the Pubs responsible for behaviour and noise, shut a few vertical drinking establishments down to encourage the others, use CCTV evidence to prove drunken louts spent a considerable amount of time in a licensed premises and that they failed to monitor their clientele. Those old enough will remember the litter from fast food joints covering our streets, once the restaurants became liable the problem was severely reduced.
Revoke approvals for any drinks clearly aimed at youngsters, whilst not every Lager lout is under 25 is a I'm guessing many are.
Replace the CCTV cameras with high resolution versions, the technology is available to get high quality video down almost any cabled video system and it is relatively cheap. More successful prosecutions will reduce offences and save money. Video & Audio analysis would reduce the need for cameras to be watched, most trouble is normally accompanied by load shouting or laughter and a crowd just watch for peaks of noise. Add feedback to the cameras, e.g. a bright spotlight that shines on the offenders so they disperse, maybe the high frequency dispersal system as well.
Zero tolerance works, if at the first sign of trouble a van load of cops turn up and make sure the offenders are prosecuted severely then word spreads. Then at least the offenders will take their punch ups & bad behaviour to deserted areas as we did when we were younger, many confrontations will dissipate before the protaganists get to a suitable venue.