Hi Stephen,
I seem to recall helping you out with this issue earlier today based on the support case that you filed, but I’ll post the solution here in case others in the same situation find this thread. The issue was that the Paypal code in your seller details profile was the version of the Paypal code that contains Java Script and is intended for use outside of eBay.
I just removed the Java Script code from behind the Paypal logo in the HTML of your seller details profile so you should now be able to post your listings that use this profile without needing to make and further changes.
I'm accustomed to using Preacticeboard.com for HTML testing as well and I have not had any trouble with it lately. However, I did a quick Google search to try and find an alternative for you and it appears Practicewriter.com may be sufficient.
If you need any additional help with this, please feel free to follow up with our customer support team using the case that you opened on this subject.
-Mike