Hi Dismounted
Thank you for your reply.
Yes, exactly that. I've posted your exact code above, and then edited the post to copy and paste the resulting code here, and this is what it becomes (although I've replaced square brackets with curly brackets as I couldn't work out how to post the code without it parsing!
{URL="http://www.yourdomain.com/"}{/URL}{URL="http://www.yourdomain.com/image.gif"}{IMG}http://www.yourdomain.com/image.gif{/IMG}{/URL}