Sorry if its too late, but might be useful to others, http://gis.stackexchange.com/questions/10808/lon-lat-transformation/14445 gives a description on the process for rotating a rotated pole grid, using some trig functions, I used this (via a python script) to convert data from a netcdf as the OP was attempting to do from a rotated pole grid to its "unrotated" form, hope this helps!
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