I've found them in 1881.
8 Court, Stafford Street.
RG11, piece 2800, fol. 73, p. 15.
Surname recorded as "Spoon[-indistinct-squiggle]" and transcribed as Spoon

Sarah's birthplace mysteriously and pointlessly indexed by Findmypast as "Stone, Buckinghamshire, England" ?!
So they were within those few streets all along.
Just the matter of daughter Harriet's whereabouts in 1851 to resolve now. Am going to look again at that LOYNEL entry. I wonder if Richard Spooner down the page could be Edward's father or another relative.