After spending the best part of the past 24 hours transitioning to HTML for my press review, I too have come across the anchor tags issue for GMail.
Completely by accident I happened on the following workaround. The great thing is that so long as links are enabled the user experience is 99% unaffected.
1) Find a web storage service that will let you use direct links, which are rarer than you think. Box, Dropbox... basically none of the boxes give you a proper direct link. I'm using Filesplat - so far, so good.
2) Upload the file and make sure it's shared.
3) Get the direct link and then use it to open the file in your browser.
4) Do Ctrl+A, Ctrl+C, then tab over to a blank message in GMail and press Ctrl+V. (I can't speak for any client other than GMail on the copying-over-images front. If you're not getting any joy on GMail I have "Inserting images" enabled under Settings/Labs, so maybe that's it.)
5) Send it to yourself to test.
The anchor tags work because... they're not anchor tags any more. They've magically become links to the same location in the file you put on the web server. So what happens is your subscriber opens the email, clicks on something expecting it to scroll down, and gets a new webpage instead. But before he can say "Oo er I wasn't expecting it to do that" he's got the exact same thing right in front of him, and of course because it's a webpage all the tags in *that* work a charm.
PS: Thinking about it, it could be that I just got lucky and Filesplat is maybe the only service that replaces anchor tags with links. Anyway, this one works... for now!