Here's a route my mate devised that we rode last Friday.
Mainly aimed at not only getting some new roads in but also taking advantage of the 20 kph+ south westerly that was blowing along the south coast we used planes (almost), trains and got buzzed by automobiles on a nice loop.
Posting here as although I live in Epsom and started the ride there it should be available to all who are London based too (you just join the route at a different point).
I can share the route on Strava but for me it was roughly:
- ride 30km to an eerily quiet Gatwick
- train to Haywards Heath (ten minutes/£6.60)
- ride 150km to Folkstone
- train back to St Pancras (one hour/£23 - regular fast trains)
- ride across town to Waterloo
- train out to Stoneleigh
- ride home from there
I clocked 207 km on strava but I think some of that was a train journey, It should be circa 190 km total.
Although I used my road bike there were a few gravel/beach sections so a gravel bike can be used too. Having said that it's very doable on a road bike but perhaps don't take your best one.
Here's my vid of the day to give you a flavour of the ride
Down by the Seaside