Thanks for the help – in honesty while stationary, the only things that run off the battery are a couple of lights, the radio and a couple of cigarette sockets for charging stuff occasionally. Everthing else is gas powered (except the spark for the fridge and heater to keep them lit). It is very rare I manage to drain the battery very low, as it charges from the dynamo while in motion. However, I prefer not to run the engine for long periods when stationary, so as not to burn petrol unnessarily or annoy other people with the noise. Also the dynamo produces very little charge at low revs.
I guess this would help maintain the battery charge if it is connected whenever stationary.
I guess it also answers the question that I would not need a charge monitor as it seems highly unlikely that I will ever over charge the battery from a panel of this size.