I have recently bought a new-build flat next to a train line. Prior to buying we enquired about the noise from the trains and were assured it was fine. We expected the passenger trains to run until midnight or so; what we did not expect were freight trains to run all night – causing disruption to our sleep.
Noise from transport is largely exempt from statutory nusiance legislation. Generally only noise caused by poor upkeep (e.g. track defects) can be dealt with using statutory nuisance powers. If you are an owner occupier housing legislation may be of some use. If you can get the noise or housing team to help by way of acoustic assessment (unlikely – but pressure through your local Councillor may help), the assessment may help when taking action against the developer.
Modern homes built next to railways should have been designed with noise in mind (in terms of orientation of living space, glazing standards and even air conditioning systems). Find out what planning conditions were put in place and whether there was any input/comment from Env Health and the Planning departments. If not, question why not. If this is a new home it should come with a warantee from the developers. Taking private action yourself to resolve this may be your best bet. If they assured you it would be ‘fine’ then demonstrating that it is not would appear to be your best way forward.