Let's say there's a directory structure you want to wget recursively. And let's say your download is occasionally interrupted for whatever reason. So, you have a whole bunch of files that have been successfully downloaded, and some that have not, but you do not know which ones.

Will using the "-c" option always successfully restart any file, anywhere in the directory structure? Is there any mechanism to validate that all files were obtained successfully? The man page is a little unclear on the issue, and gives several provisos that indicate that there are absolutely situations where you're going to wind up with a corrupted download.

And is there a way to tell wget to check the size of each existing file against the source, and if it's different to just delete the local copy and then re-download it from the beginning?

Try using this:
I know that the code above is far from perfection, so try fixing it a bit.
A little explanation:

• The first line ("for" command) reads the list file per line (with "cat" command), putting the content of each line into the "x" variable.
• The third line ("if" command) makes sure that the file does not exist.

Don't forget to replace the text inside brackets ("<....>").

Hope it helps