Let me know what time you're likely to be passing through and I could wait for you
here
There looks good.
Personally, I'm not keen on Westerham Hill, and there are various other ways over the ridge. You don't have to go past the grim reaper. If you go straight on in Downe village rather than left towards the reaper and then go left on Jail Lane it brings you to the top of the grim reaper hill, but not as steeply (steep, but not as steep)...
Church Hill? Funny you should mention that. I've never actually honked up it, and just assumed it's worse than what we're calling grim reaper hill. If I recollect correctly it's narrowish and busy enough (nothing like Westerham Hill of course) that a slow ascent might not be the most relaxing experience with cars on our tail, but it's not that long, and overall it would surely save a bit of time without sacrificing any real points of interest. Prefer it to the western approach. I'll do it on the recce.
Consider going up the hill after penshurst place then via groombridge, town row, Mayfield, along newick lane to heathfield then along the cuckoo trail (old railway line now a cycle path and utterly flat) to hailsham then out through the marshes via downash and rickney then past Norman's bay to Hastings. This is far flatter and faster than the route you plan. There is also a pleasant bit of coast to ride alongside.
I like going via Bidborough because it offers such a great vista north, and sets us up for a fast spin through Southborough then Tunbridge Wells.
At first glance T Wells might seem to be a place to avoid, but as we'll be getting a large serving of country, I think a brief dip back into town midway through the ride helps keep it from being too samey after London. Although the route I've chosen is the main road, it's not too bad, even with traffic; the bus lane through Southborough helps. Plus it's a good place to get food. I'm planning on stopping in the precinct for lunch.
Your Cuckoo Trail variation is flatter, at least the Cuckoo Trail part (and maybe some other bits; I don't know that route well enough to compare), but I prefer the very pretty lanes between Brightling and Herstmonceaux, former site of Royal Greenwich Observatory, which we won't be running into but will be able to see from a distance. From there it's mostly downhill then downright flat, with a great warmdown from Pevensey eastwards, ending with a spin along the boardwalk.
For the train journey back you may prefer to put 20p in the Permit To Travel machine at West St Leonards station, which is usually unmanned, and if asked pay the fare to the ticket chappie on the train. If asked. Starting from Hastings means you must buy a ticket to get through the barrier.
Just sayin'.
You can also get on at Warrior Square, which is often manned but also without a barrier. Speaking of trains, the Hastings line is usually pretty mellow. As for not paying Southeastern their due, I can of course offer no comment, other than the observation that once you get north of Frant it's all barriers (not always closed it must be said) and penalty fare stations, except for High Brooms I think. But I've never had a problem buying a ticket on the train.
We did a club run from Croydon to Rye, ending up at Hastings for the train home earlier this year. It was utterly flat*, gorgeously jaw dropping and mostly on very quiet back lanes. Rye is somewhat more beautiful intermediate destination...
I'm not particularly trying to flatten the route, though I'm not averse to shaving some miles; just not at the expense of the more interesting bits. Plus, I know this way well enough to feel comfortable escorting others.
User10571 – No, it's Hastings for me. Don't know what route Adam used, but I'd be surprised if it was this one!
As I was posting, StuAff put up Adam's route. Am giving it a look...
...and now that I have, I can see that it's doubtless faster, but offers a totally different experience.