At our age I may well have read, but there's no guarantee of clicking through links or memory or understanding. :tuttut:

Finally got around to buying and using some Sugru.
The lower (body) grommet on that pipe is also falling apart on my car, though only half of the top face is currently missing.
Cleaned it up and repaired with Sugru today.

If it works OK I'll attack the other (boot lid) end as my solution using black mastic is starting to get too hard and crack. It's lasted a fair while but clearly doesn't have that much life left now. The extra cable-tie support I added after rerouting slightly has helped though. ;)

Checked it this morning, feels firmly fixed, well-sealed and resilient.
Not the tidiest job, but acceptable for where it is and the difficulty of accessing all round.

Looks fine to me. Nicely done! +++