Hi Kor,
Thanks that pointed me in the right direction. Here is what i did in case helpful for anyone else. It was the page called ‘GD Archive Item’ that needed changing. I rooted out the code that brings in the description which is [gd_post_content key=’post_content’ limit=’60’ max_height=’120′]. The ‘post_content’ is the field key. The field keys are generated with the settings section of Places (or whatever Post you have) in the custom fields tab. I didn’t know how to create a shortcode for the blog excerpt so I created a new text field and replaced the second post-content with this new field name. I now can write short snappy headlines. All resolved.
I actually think they grey is jsut the fading of the text behind the Read More text so my last question is how to I define how many characters of the field are shown. Look at this item https://christmassy.co.uk/destinations/united-kingdom/greater-london/london/churches/st-pauls-cathedral/
as it displays in the archive