And a Happy Christmas to you Mike. It was lovely to meet you yesterday and thanks for fitting me in before Christmas. You may be interested to know that I got 38 mpg on the way to you and 43mpg on the way back home, so that seems to be an added bonus of the NA kit! (Same journey, similar drive etc).
p.s. The part number for the Subaru 'Door Mirror Auto System' kit we talked about was 484-010-006 from japanparts.com ( https://www.japanparts.com/parts/list.php?skwd=484-010-006&x=32&y=11). It was about £75 plus some import tax.