A solution which you might want to consider at minimal cost, though non-Garmin if you want portability, is a standard iPaq-type PDA with a GPS mouse, running an open source gliding program like XCSOAR.
I mention this because if you already have a PDA you can buy a GPS mouse for £20 or so from eBay and try it out. Fits easily into a car phone suction mount which can attach to the screen.
What you get from the software is a moving map which you can zoom in and out, airspace configurable to appear when close and disappear when not, logging in .igc format, ground speed, climb/sink last 30 secs, height AGL, height GPS, track over ground, track lines for your entered route, and a whole load of other configurable stuff to do with gliding that you're probably not interested in. Terrain files at various levels of detail can also be added in, all for free.
I run this setup on my glider, though with a Garmin GPS 12 (always set on the "That way, stupid!" arrow), and it's worked with no glitches for the last 5 years or so. However, my system requires two mounts and a connecting cable, so would be less portable.
I know someone flying with the GPS mouse setup (just rests the mouse on top of the panel), and he has had no problems with it.
The downside is you don't get the CAA chart, but the upside is that you can turn on/off different terrain features - I prefer a pretty uncluttered map which gives me airfields, major towns, railways and major roads.
From what I can tell this kind of setup offers much greater and more flexible functionality than the functions built into all but the most expensive Garmins. However, it's only of any real use for VFR flights.
I believe one or two power pilots have started using this - maybe one of them will read this thread and say whether it's suitable for their needs.