Indian independence had been on the table for years. People were used to the idea - plus one of the main justifications for imperialism was that the subject peoples weren't fit to govern themselves and the colonialist powers were bringing them under their protection until such a time as they were. So independence in a way was far less damaging to Britain's self-image than the sale of a colony largely composed of Brits - one is a natural progression along the colonialist road, the other is a down-and-out admittance of decline and inability to govern.
I think the Attlee government would far rather enact temporary cuts - for example in the armed forces - than permanent sales. Regiments can be reinstated. Colonies cannot.
Greece and Palestine are also very different in the sense that they were temporary occupations or mandates. Britain was never meant to be there forever and had never said they would be.
