Hi Luke - this sounds like what I need to do (you're right to assume they're tiffs, sorry for leaving off vital info).
I need to ask some follow-up questions.....I'm new to gdal code and have not really used much code beyond arcpy.
How do I run this code, is it python?
How do I know if I have a working GDAL install? - I have lots of folders on my computer called GDAL in amoungst program files for FME, Arc and QGIS - the gdal website goes over my head somewhat.
Thanks
Ben