Exposed, coastal, balcony!

Hi all
I am a newbie hoping for some assistance. I live on the second floor, facing SW, on the sea front. I have been trying for a couple of years now to grow Aubretia in small window boxes, I have tried seeds and established plants with no/very little success. As this is a rockery plant and grown in the Brecon Beacons I thought it would be fine!!!
I want something that is mat forming, possibly cascading, evergreen and something I do not have to replace every year. Due to my location I understand that the wind and the salt are going to hinder me somewhat but, I just want my balcony in bloom!
I would be grateful for any assistance or suggestions and look forward to hearing your comments.
Thank you

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.