thetowers has given you a good explanation.
Marriage certificates are likely to be the best sources of information as the bride and groom give the information themselves and they usually know the facts. Of course, there is no guarantee that the 'facts' they give are correct!
It is also worth remembering that the need to produce identification is fairly new. Before Medicare you fronted up to the hospital, doctor and told them your name, no need to prove who you were, so you could be using another name very easily, both in giving birth and in dying. No need to prove your ID for marriage records either. And, even recently, when I gave my aunt's details to the undertaker to be forwarded to the registry no-one asked for my ID, nor for any proof that I was giving the right information. Of course they knew my aunt's name but her parentage details were just on my say-so.
WW1 and WW2 enlistment required no ID either.
As for different spellings of names it's very common. Nowadays you fill in forms yourself but in the past the registrar asked for details and s/he wrote it on the form. So it was easy for a name to be mispelled, especially in early days where illiteracy was not uncommon. Handwriting was used in most cases with some letters looking the same eg your Rowling/Rawling. Then the original form was transcribed into the index allowing for more possible errors. It's not unusual either for names to be mixed up - for example, the registrar might ask for name of mother and the informant is unsure which mother is meant - the baby's mother, the informant's mother etc. It's a wonder any of us can find anything!
The other thing to remember is that an index has very limited information so certificates are often needed for better information. Usually an index gives the place in which the registration was made - it is not the actual place where the BMD occurred.
Cheers, Judith
