Well I went out and attempted the route I had planned...
https://www.strava.com/activities/257846526
Stopped far too many times (8 or 9!?) Mostly to put on/take off my boil in the bag rain jacket. I went out with normal jersey and thermal one over normal bib tights with shorts on top, there's was a constant gusty strong wind even though the ambient temps were okay (5-8) making it feel more like 3-4 degrees. Crossed the river cold so put my boil in the bag rain layer on for some wind protection.
My usual run out to Mordiford went okay but I knew I was gonna overheat as soon as I got near any hill. Turned at Mordiford towards Woolhope and I was out of familiar territory, could see the first CAT4 8% in front so stopped to strip off my rain layer and nosh some haribo ready.
Probably stopped too long as I got too cool, started the climb but overcooked it trying to warm up so then overheated and had to stop. Failed to get going again and fell as the mud on the road caused my back wheel to slip on my downstroke and I couldn't balance. No proper damage (except to my ego) so I set off again.
Finished the main on followed by a few smaller climbs but none as hard as the first, as this was the first time i'd used the 810 for navigation I took a wrong turn at the top so stopped to get my bearings and figure out the 810's 'map' (it's useless to try and orientate yourself with isn't it?!).
Almost turned around and went back to the route I knew but soldiered on towards Woolhope itself, reached a T junction I wasn't expecting and no signposts... Followed my nose and came to a signpost for Fownhope (my next waypoint) and then the Garmin map made sense! Took it easy as knew there was another hill soon, had to stop and put rain jacket back on so paced myself to Fownhope... No hill!
Back onto a more main road then heading back towards the route I knew, stopped at the bridge near Holme Lacy to eat chocolate and take rain coat off (munched my chocolates as was starting to flag...) as knew there's a 10/12% short sharp hill just before Holme Lacy.
Paced myself up the hill which gave me some false confidence so instead of taking the easy route home (I knew) I headed back into unknown territory for the next hill, another CAT 4 which reaches 12% midway through the 2.5 mile climb.
Blew up royally and had to stop, was angry with myself so attacked it again (stupid!), blew up again and had to stop a second time in about 15 meters lol. Berated myself and waited until i'd calmed down and lowered my HR enough (140bpm) before setting off again, paced myself in bottom gear and ground it out at 80rpm until the top.
A few spots of rain returned and as I knew i'd done most the climbs I stopped to put my jacket on again, eat my second haribo and let the Mrs know I was on the home straight (just 1 climb left).
Paced myself through a couple of small descents and was prepared for the last climb, ground it out in bottom gear and knew when I reached the top that it was all descents home. I was back onto a road I knew so hammered out the descents as fast as I dared and overtook the only other cyclist I saw the whole ride. Made it home but not much left in my legs.
I'm glad I stuck to my route even though it was probably foolish, at least I know the route now and where the real hills are. Several of the CAT4's I had to grind out (60-80 rpm) in bottom gear making me think I may need a lower cassette for any other attempts, at least until i'm better trained for them? 23mm tyres was a poor choice for the mud and conditions but the 25mm's I have I know would've been worse! I also need to dress properly - ideally I need a jersey with some wind protection so I don't need to wear my boil in the bag rain jacket for it.
Sorry for the long post, I should probably start a blog!