There is this coffee shop
Instead of riding into the centre of Brighton like most London to Brighton weekend club runs. Turn left after descending Ditchling Beacon onto the Lewis road (fairly fast) near to Sussex Uni.
At the mini round about outside the uni turn right onto The Drove and you'll then pass Brighton uni on your right.
You'll have to ride one more final climb, it had a constant gradient and easy to find a rhythmn.
It is absolutely worth it, firstly you don't end up weaving into Brighton through all the traffic, dodging people from Crawley who has gone to the 'seaside' for some slot machines.
Secondly, more importantly, you get an amazing view that if you aren't puffing already, will take your breathaway.
Descend on the Falmer road through Woodingdean and into Rottingdean. A cute little village along the coast from Brighton, complete with 17th century pubs and buildings, village duckpond and stonewalls.
When you arrive, find a place called JaJu Beans & Leaves. They mostly sell coffee beans and loose leaves for tea you home brews rather than bee a full scale cake stop. That said you can still pick up an espresso before you head back to the capital.
I've been (no pun intended) sampling their ground coffee selection in my Moka Pot recently and in the latest batch a small packet was slipped into the bag, ethnically named 'Ethiopian Yergacheffe'.
So, if you are looking for new coffee or a reason to ride to Brighton. There you go
(if you take the train back to London from Brighton, there is a bike bath back along the cliffs into town)