No other folder is good enough to do that distance.
apart from a birdy – done the 35 miles home on mine before with no problems, apart from being saddle sore as I hadn’t ridden for a while as I had only just recovered from a kidney infection.
With the sport stem the position is not upright (it is with the comfort stem) and is quite similar to a mtb, esp with Big Apple tyres. It is fast and fun to ride.
However the requirement to use a bus really ties you to a Brompton, as nothing else folds quite as small and getting on a bus with anything bigger might be problematic in rush hour.
So have a look at the S type bromptons.
And several people do the london to brighton on bromptons as well.