If you already have a Pilot III then you can get a very good solution quite cheaply. Buy the cable as suggested by Mr W (or any other, but definitely go for one which doesn't require piggy-backing a series of adapters) and use it to hook the Pilot III to your iPAQ. Then run MemoryMap on the iPAQ with the CAA charts. Use the Pilot III for navigation on planned routes but have the nice moving map display of the iPAQ.
WinPilotVFR is similar to AnywhereMap in using vector based maps and a database of navaids, airspace and airfields. It is slightly less functional than AnywhereMap, though it does provide all the most essential stuff. When I tried it I had some stability problems, but it may have improved with newer versions.