I've since seen a variation of this rumour to the effect that the Post Office were trying to 'push' the 'non-religious' angel Christmas stamps so that sales of the 'Madonna and Child' Christmas stamps would be low and that they could claim in future years that there was no demand for 'relgious' Christmas stamps.
Dave Faulkner contacted the Royal Mail about these rumours. You can see his latest post on the subjet here. The text of the Royal Mail's official statement is reproduced below from Dave's blog:
We have become aware of an incorrect assertion being made about the motives behind the sales of our Christmas stamps. There is absolutely no intention on our part to suppress sales of the Madonna and Child stamps in order to be able to claim there is low demand for religious stamps in future years. Indeed, we have produced tens of millions of them, and we want to sell them!! We have given publicity to both types of Christmas stamps, and the availability of both has been widely covered in the national and local press. Furthermore we plan to have the Madonna and Child stamps available every Christmas in future, alongside each year's "special" set, which will continue to alternate between religious and secular themes.