Found the answer to my problem.
I found that one of my ihtml templates had the following entry:
<input type="hidden" name="MAX_FILE_SIZE" value="64000000">
which is in fact separate from any PHP settings and that was the reason for why I was having problems uploading multiple images through my web browser.
This is what limited me to 64M rather than the 650M I had set through PHP.
I simply modified the value in my template and all is fine again.
BTW this has nothing to do with SME server
