So I did a quick bit of flatting back, and here are the comparisons to the RAL colour swatches.
On the left is the colour I thought I was getting. In the middle is a bit of flatted spray paint delivered. On the right is the 6011 that I will probably go for. The delivered paint in the middle is slightly more blue than the RAL swatch.
I could send back the two tins I still have (I need to do the doors as well), but not sure I can be @rsed for £22. I could order the 6021 from somewhere else, but that may be no closer. I will probably go for the 6011, and get one can to try it out first, which would have been the wise move first time around.
Maybe I should go for that Scottish flag blue?