snip
Basically I am looking for a very good VFR GPS. Especially now that
Jepp have dropped their Flitemap product, so there *appears* to be no
way to display charts containing elevation data on a moving map GPS.

Depending on your budget, you might be interested in
ChartCase running on the Motion LS800. It's the same
screen, I think, as the AvMap IV and is pretty spectacular.
I'm not sure about the size; I think the AvMap is thinner.

ChartCase gives you a complete desktop flight planner plus
all the NACO charts (hi, low, WAC, sectional) and plates for
the US, all georeferenced. Even the airport diagrams are
georeferenced.

On top of that, V3.0 will give you synthesized flight
instruments and georeferenced LandSat imagery. You can
actually fly "contact" above the clouds, watching the lakes
& forests go by underneath!

And, yes, there is a TAWS screen and a WXWORX option.

http://www.flightprep.com/rootpage.php?page=HomeEFB

seattleavionics.com just introduced an apparently-similar
product, but I am not familiar with it. I was/am a beta
tester for ChartCase 3.0. No pay. No freebies. But it's fun.