What can I do about the noise levels from the pub next door?
Noise issues are surprisingly common, but under the law of nuisance you may be able to apply to court for an injunction to stop the noise. There was a recent case in which a flat-owner was held liable in nuisance for causing excessive noise for the flat below. However, in the same case it was held that the landlord of the flats, the freeholder, was not liable, which may be relevant to your case, which involves the brewery (the freeholder) and the licensee.
The full article is available to subscribers of The Times, here.