UK Postalcode areas filled map

Hi,

I wonder if you can help with this one.

I am looking to create a filled map like the one in this image:

My data looks like this:

I can get the Map to fill when I insert the Postcode plus the numbers (in the first column) but not the two digits only, which would work better for what I am trying to do.

Is there a way to do this?

Many thanks.