Thanks for the posts everyone.
To JJen - yes that's the correct Hughes family in 1901, and I do have the birth cert of Evan Hughes which states that his mother's name was 'Elizabeth Hughes formerly Pierce', and the birth address is 94 Hood Street, Bootle, the same as the 1891 Census street address.
I have to admit that I didn't check the GRO until you posted your message, and so did not know about the Killean references - sorry again for not checking my facts properly.
I don't understand the Killean link - needs further thought.
To Heywood - yes I believe that is the correct George Hughes in 1881 lodging in Birkenhead and working as a Railway Inspector.
To Hallmark - regarding the Pierce family, I think that James Pierce married Mary Ann Murphy - his Probate record gives his wife's name as Mary Ann, their son John's birth record shows her maiden name as Murkley (sic), and James Pierce and Mary Ann Murphy are the parents of Joanna born 6.10.1844, Mary born 5.4.1848 and Phillip born 14.4.1846). Of course there could be a James Pierce that married Mary Ann Murphy and another that married Mary Ann (surname unknown).
I've only been researching the Pierce family for a couple of days, and have found baptism records and family members in 1901 and 1911 - James' sons Martin who married Mary, and John (described as Foundry Proprietor) who married Susan -and they are in the right locations (Maudlintown and Ballyboggan).
I was hoping that there might be some source local to Wexford, or some expert in Wexford, that could shed more light on the Pierce family, in order to determine if there was a child called Elizabeth born around 1843/1844.
Thanks again for all your efforts on my behalf.
Brian.