There used to be a market for economy trips to NYC on a non daily basis, however the huge growth of legacy long haul connectivity killed that stone dead. Why pay a premium to fly on an old American Trans Air TriStar once a week when BA/KLM offer multiple daily frequencies on a more comfortable product.
A weekly shopping flight is all economy, a daily offering would demand a better balance of business and leisure. In terms of the UK, EDI has huge inbound market presence, GLA less so but still high and MAN has a lot of business it terms of the leading regional airport. BHX just has a single UA flight to Newark and LGW can't hang onto a single JFK as LHR being so close just kills it, less so but similar for BHX.
IIRC were there not CO routes operated with B757s between EWR and BRS, BFS, BHX, MAN, EDI and GLA (but not NCL)?