multiple same set columns

I have two columns, they are postcode prefixes (UK), so I have 147 postcodes, but I want to go from each postcode to the other. so, for example, W1 postcode to all other 147 postcodes, including W1.

So I will have W1 to W1, W2, W3 etc, etc to W147 (using W1 to W147 is made up but it is easier to describe this way)

Then I want to go from W2 to all postcodes, but I have already got the row from W1 to W2 so I don't need to have a row with W2 to W1

I already have a sheet with all the variations on it i.e. W1 to all postcodes, W2 to all postcodes, W3 to all postcodes, there are 21k's worth of values. 

So how do i remove the rows where the i have duplicates?

below is the actual values 

as you can see i have BR1 to BR2, so I don't need BR2 to BR1

how do I find and remove these duplicates?

I've hunted about and don't seem to be able to find anything. I've attached the file. 

Thanks

Jon