Thanks Meursalt. Wakeling's not my surname but a reference to where I live - close to Watling Street which is derived from the waeclingas, the local tribe in roman times, so I updated the spelling.
I found three versions of the poem.
Last word is 2-4 in one and fits the extra letters we get in 16d and 18d.
The next word is also 2-4 and 5 letters have to be changed to make this 6 letter word.