The UK is like that...high costs, high taxes. Such is the reputation. By making a connection in LHR to a domestic flight, you're exposing yourself to more of it.

Taxes come out to about $105 if you did a non-stop EWR-MAN, for example. That's the only way I know around some of it, and of course your same fare may or may not be available.

While I agree that taxes are out of control, and I would like to fight it (if there's something that can be done), I'd prefer to address U.S. taxes/segment fees/PFCs, which can amount to 50% or more of the fare actually paid.