Anglian double glazing

Moved into a house with aluminium DG all round. Most window handles don't move, and the gap between the glass and the frame is black with fungus. Any ideas how I can release the handles get rid of the black ? TIA,. |P
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Our aluminium DG's handles have little grub screws in them so you can lock them (yeah, nice and user friendly!). Is it possible that yours have got the same and they're done up at the moment?
D
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