One more for the highly coveted 'Grimpeurs du Sud' badge.
The Down to Downs route, available as a permanent, is wonderful at this time of year. I rode it yesterday and the views of the North Downs and over Ashdown Forest were magnificent. There is enough greenery to make the scenery feel alive, but not so much foilage on the trees as to obscure the views.
Despite the 1.75AAA it's rather a benign 110km: long, well graded climbs rather than the "short sharp" gradients on some of the other rides you mentioned. Once you get Toys Hill and Vicarage Lane out of the way in the first 15km, the rest of the climbs are mostly harmless.
Other than a few stretches (the main exclusion being the road to Bough Beech after descending from Ide Hill) the Kent and Sussex road departments have been out and about laying down some lovely tarmac or patching up potholes. The Ashdown forest roads and the descent to Groombridge, to name two in particular, are much improved in the past 12 months.
The only thing I think could be improved on the route is the short stretch of A21 on top of the North Downs, although this can be avoided by using the cycle path on the south side of the road (or, I suspect, but have not yet checked, by taking a detour on the back roads of Green St Green).
There's a steady flow of entrants to the ride, such that out of every month there is usually a couple of riders who do it, if you prefer to ride in company.