Peterlondon,
To put it simply, there are no justifications as to why Lhr crew earn so much more than Lgw crew. The company's line is that "to remain competetive and Lgw is in direct competition with Lo-Co's...bla bla". Still doesn't make it right. Also, Lhr crew get London weighting, whereas we don't, as we're 200 yards within the wrong county. But such is life. There will be a difference for ever, pretty much, and I've come to terms with that a long time ago.
Gg