Just to keep you updated, I have changed over to 802.11a at 5Ghz.
The 2.4 Ghz 11.g was interfering badly with my video transmissions on 2.4 Ghz, whatever the channels in use.
On my walkabout test, 11a had the same line-of-sight range as 11g, about 100 mtrs.
11a did not suffer from the link breaking while I was moving as did 11g (see previous post).
This would indicate that 802.11a is a better choice for moving robot control, and essential if you want to also use a video link from the robot.
The 11a link did break when a large bush was in the line-of-sight, 11g did not.
Only simple tests that need to be backed up by others but an indicator as to which system to use.