In the end even dazzy.p and myself didn't make it to the mountains. dazzy's front derailleur was shagged and would only move into the small ring with extreme physical force directly on the derailleur. We turned back about 6 km from the Family Mart.
I had never intended to finish it, but I hadn't started intending to even ride as far as I did. Left my arm covers at home and now have really sunburnt arms as a result. Dumb. And my power meter crapped out on the way home. May be the battery, although it didn't just stop which is the usual form for battery induced failure. Anyway did a master reset and will see what happens next time out.
Now getting some serious maintenance done at Seo in Omiya. No more rusty chain, stuck front dérailleur or slow puncture next time. All I need now is the legs to be in better shape by the time we reach the climbs