Further update regarding the solar rear camera. if you buy direct from their website, it's cheaper than the large river website.
i drove the car away from the caravan and it remained connected to the camera for a good 50 yards or more. good quality picture too. will be using it in anger this weekend on a trip to france so will report back on stability etc.
i definitely need a second camera as the angle of view and tilt available for a single camera is limited. the monitor i bought is able to pair with 2 cameras, so that should be possible. wish i'd know when i'd bought them (not an option on Big River to buy 2 cameras & 1 monitor, but it is on their website) as it would have been very much more cost-effective (only an additional £20 rather than the £80 it appears to be to buy the camera on it's own.)
it's frustrating that the monitor only stays on for a max 120 seconds - seems a bit of an oversight by the manufacturer considering it's plugged into the power socket in the car all the time.