OK, having scoured Liverpool for Prescot Street only to find it listed under the West Derby District, I then personally knocked on every house - about 200 in all I'll have you know!

and interrogated the families about any Johnsons or Robertsons in the area, all without success. I conclude:
Alice and family in London in 1861 ARE our family and were enumerated there for the census, subsequently returning before the end of May to have Jessie christened in St Peters. At two and a half years old I bet the little brat ran all over the place and squawked when the vicar chucked water over her head too.
There are any number of deaths for father Charles Johnson before 1871 so you can take your pick.
Just one thought, if young Hugh Moody was born and died in Mile End to this family, then they did an awful lot of moving about.
HOWEVER, how would it have been if Alice and Charles Johnson just came home to visit family and got Jessie christened while they were home, after all St Peters is a prestigious church and maybe they saved it up.
Blast, I've just remembered I was supposed to look at another christening on 27th wasn't I while I was there? I know somebody's going to bring that up and it completely slipped my list before I went as I only had an hour and wanted to cram in quite a lot of things, sorry! and now I can't even find the other one which was the day before.