Fascinating responses all of them - thank you all so much.
Here's the bigger file on my website if anyone would like to view it as a bigger picture.
It's about 450K, so if you have a slow connection it might take some time!
I think apart from obviously assisting me it's worth looking at to see just what one of these things actually looks like. Hopefully that will inspire those of us searching here to keep going...
Again, thanks for the help, and if anybody can add anything else that will be great.
Edit: Oddly enough, if I click the link directly the picture is small, but when I copy and paste the URL into the URL window the picture is large. Something to do with the forums set up perhaps?
By the way, if this birth certificate is indeed from 1918 AND from a Polish teritory then it's pretty special in itself.
I'm definitely going to include that information in the 'Polish roots project', so thank you.