Oh yes, I can empathise with that one. All the people you COULD have asked, and didn't.
On the other hand, many of them wouldn't have told you much, and lots of them would have passed on somewhat garbled memories. That's what we all say here.

I've found Lilian Maud Tabor in the 1911 living at 32 Beecholm Road, Clapton. The family have a lodger living with them, and, reading between the lines, I bet that's how Lilian (a dressmaker) and William Henry E Wilkinson (a stockbroker's clerk) met.
I've tried to see if I can see William in the 1911 in Clapton or thereabouts, but no luck currently.
The thing is, of course, that many marriages weren't happy and, unlike today, you couldn't just divorce and move on. So people did leave.
You may have to content yourself with putting as much meat on the bones of William's family as you can, and resign yourself to not being able to track down much about the man himself. Unfortunately there are rather a lot of William Wilkinsons in the WWI records, and beyond those, tracking people in the 20th century is very difficult.
On the other hand, didn't you say that Lilian DID marry later, so it may be worthwhile looking for William's death around the time of the marriage, as perhaps she did know vaguely where he was, or was told about it?
oh, sorry, re the marriage, told you everything else about it, but the year! 1883!
Have also found Clara Jane Mostran's christening records, parents shown as Edward Balls Mostran and Frances Jane Clark Mostran. Edward's a porter in 1860, rather than a herbalist.