Goodchild

[lizdb]

For the sake of £9.25, you could be sure , rather than risk following the wrong line and either wasting a lot of time and money if you ever have to re do it all, or alternatively remaining blissfully unaware that the ancestors on your tree are actually not related at all.
"Have been told", " seems to be", "a hunch" etc can turn out to be unreliable bases for research!
As we have seen on this thread already, co-incidences do happen (eg the 2 Percys dying in the same hospital in the same year, both with wife Gertrude), so it isnt beyond tbe realms of possibility that 2 Percys could have had a daughter that died young and ended up in Sussex.
Up to you , of course, and I do agree that with this new information tbe Croydon one appears to fit better, but it were me I would be buying tbe birth cert of one of the twins before going any further! 

[groom]

I strongly endorse all that Liz has said, the birth certificiate is a must. The thing that worries me is that the parents and the two older children were born in the Croydon area and died in Sussex, yet the twins you say were born in Ipswich, where there were other Goodchild/Johnson families.

Of course, it is up to you, but I know what I would be doing next!