Well I sussed the .DDS config, and after only once saving the image upside-down which gave a whacky result I'm nearly there.
Now I've seen it in the (virtual) flesh rather than just a photoshop template I can see what needs tweaking - darken the blue lines and wording, line up the chequers and the jam sandwich on the doors. I may change it to Humberside Police as it's more in keeping with their colours.
Any other constructive criticism here would be helpful.
