FAILURE!!!!!
I couldn't do it. It's only 600 m, and I got to a point where I thought my heart was about to pop out of my chest, so thought I'd better stop.
Because the road curves at that point, I couldn't see how close I was to the top, otherwise I would've forced it (I say now in retrospect). After a short break to catch breath, I hopped back on the bike to find I was only about 100m from the crest.
Weather & time permitting, I think I may give it another go next weekend. My gearing 30 x 25 makes the climb very do-able, so its just a matter of fitness (and mental toughness).
coming back down, I found it a bit scary, so I may get a new pair of brake pads before the next attempt. I defintely wouldn't try coming down that hill in the wet (but then, I'm a bit of a chicken).