:It needs to look interesting for as much of the year
: as possible, as this is what we see from almost all windows, it needs
: to thrive on a North wall, in fairly acid and often waterlogged soil,
: and it shouldn't be too dark....

I would try honeysuckle

One of the fancier evergreen ones? But which one is pretty for and not
too rampant for a 2-m trellis?
Klara
--
damp and cold in Gatwick basin