The spam/failed orders seemed to have stopped for the time being at least. I will go through the anti-spam log and mark each entry as spam or not spam accordingly.
Anyone any ideas. I have deactivated WP Super Cache plugin as I thought this might be the problem, but still the same issue.
Instead of <td><align=top">We offer free...... try <td><valign="top">We offer free......
Would you be able to post the code you are using?