Good work Jo.
The steepest bits IMHO are (all relatively short):-
a) a few short sharp snaps outside Cheshunt (both directions)
a.5) Bullocks Lane climbing into Hertford and Port Hill climbing up to Bengeo
b) Lincoln (Southbound only, if it goes the way I think it does)
c) The climb up through Crayke and again up to Coxwold (both dirs)
d) After the bridge at Whorlton (although it wasn't as bad as I remembered it from the Border Raid, north only)
e) A couple of bits of Yad Moss, just after the ski-lift if I remember correctly (north) otherwise it's a tame climb, just long
f) Coming up through Alston Southbound will be a tough one (south)
g) The insanity between Canonbie and Langholm that isn't on the route thankfully.
h) The first few snaps after Langholm (north) I was starting to worry that the whole of the B709 would be like these.
i) The A7 coming southbound until you turn off onto the B roads, especially if it's a busy time of day.
The climbs on the B709 going North are a nice gradient for fixed climbing. Coming back they're shorter (and therefore steeper).
If I do sleep at Eskdalemuir I may leave a bunch of stuff there whilst I nip up to Dalkeith and back to save me lugging it over all those hills. If that's allowed of course, otherwise I'll just stick it in a nearby hedge.
The steepest is probably Crayke.