Thanks Garry.
Over the weekend I managed a few colour frames in between the clouds and played around with CCDSoft's facilities for handling them - the main thing I need right now is more exposures - I don't have enough to get a reasonable feel for the colour processing stuff. It looks like the CCDSoft stuff will be good though.
Re photoshop & FITS ... I think the main problem is I have PS v5.05 - if I had CS2 or something I think it'd be quite easy.
It's anoying that CCDSoft can't export to 16bit TIF files, or perform curve operations on a FIT file, either would solve my problem without me having to fork out the cash for a PS upgrade
Roger.