If not, is there enough room behind a tumble dryer to turn the vent
hose through 90 degrees where it comes out of the appliance and have it
coming out sideways at the rear?

I haven't had a crappy vented dryer in years. Buy a proper condensing one
and you don't need an inconvenient hose snagging and kinking. You also don't
need an ugly hole in the wall that will be in the wrong place/size for your
replacement model.

I have a Bosch 6920 integrated tumble sensor dryer. It is absolutely
brilliant. The filter works really well, it has a outlet pump and came with
the drainage kit free. Sensor drying is such a convenient cost saving
measure. No air hose is required. It collects water very well (it used to
fill the huge tray every drying cycle, even after a 1600 spin which left the
clothes feeling quite dry), with no obvious increase in humidity or
condensation in the room. It was in a different league to my previous Hoover
condensor.

Christian.