did Bert Lloyd,touch this up?

When you say touch up I am not sure what you mean.

There are 14 versions of Tam Lin in Child. It has innumerable spellings and pronounciations.

There really is no definitive version of it to "touch up".

If you mean did he put together a version with verses and structure from other versions then he certainly did. He may not have revealed what version(s)he used to make another version. His privilege I would have thought.

It is only "Bert Lloyd's version" in the sense that he sang the one he put together(you can hear it on Classic Bert Lloyd, Fellside) and others may have copied it.

People do this all the time. As far as I am concerned it is the folk process.