If it's the crap bosses that are causing the depression, contact the TUC at Congress House in Great Russell Street. I don't know what sort of workplace you've got, but there's no real reason why you shouldn't have the support of the relevant union behind you.
Saint Tony is, after all *supposed* to have made the workplace more union-friendly and certainly, after some time licking its wounds in the post-Thatcher doldrums, the TUC is currently reshaping itself and is proving seriously useful in such areas.
If the union path is of off-limits, try the CAB; they will have the pertinent bits of the DDA on file, together with a non-lawyer's digest explaining the ramifications of the Act for idiots like us. They may also be able to recommend a local legal firm that specialises in disability-related cases.
Whatever happens, good luck - depression is one of those things that everyone takes the piss out of until they get it.