Excellent, as commented previously.
This time around I was pleased to discover that one can substantially improve on walking-time to Arno’s Grove Tube, by catching one of the two pretty frequent buses (184 & 298) that ply between Waterfall Road and Arno’s Grove Tube.
Counter-intuitively the buses from Waterfall Road to the Tube travel uphill towards Betstyle Circle — away from the Tube’s direction — but then do a U-Turn and come back down Bower Road (?) to the Tube. Quite a time-saving tip!