amend wrapping around side widget

You can use custom CSS:
https://adinserter.pro/documentation/alignments-and-styles#custom-css

Use Preview window to visually adjust margins:
https://adinserter.pro/documentation/code-preview

Widgets may have additional margin/padding defined by the theme you are using.
To change this you need to override theme CSS.

I selected Custom CSS and changed the code to the following:
margin: 0px 0; clear: both;

The top, left and bottom margin reduced a little but have a wider right margin.

Unfortunately, I dont find the Preview window very useful as what it shows is completely different to what I see on my site.

Have I done the CSS code incorrect, or its now my Theme causing this?

The Preview window shows only ad code with wrapping div.
Margins and padding for block 2 are like you set.

However, code block 2 in placed in the sidebar.
What you see is widget padding:

This is defined in the theme styles.
You need to override styles for this widget.

Hey, you can try to cancel theme padding with negative margin.
Try custom CSS for block 2:

margin: -20px 0; clear: both; text-align: center;

Thanks for that code. It did remove the top and bottom margins but still has a left and right margin. (you can check it on my website now).
I think its better with all 4 margins until I figure out how to override the widget style.

Space on the left and right is because the width of your image is smaller than the width of the sidebar.

Ok, thanks.
I thought that if all the affiliates provide banners/ads in standard sizes, like 300×250, it was so because to fit in the side widgets. But now I see that is not the case.