3 door Freelander GS Td4 - Intermittant Immobaliser fault.

My Mrs has just bought her first Land Rover, its a very tidy looking Freelander Td4, the 3 door version. It runs really nicely, (for a Land Rover), and it does approx 100 to 140 miles a night travelling across Leicestershire as she is a District Nurse. The Immobaliser was playing up, it was flashing the red light really fast, so I put a new battery in the remote and that cured the fault for 99% of the time, but very rarely the Immobaliser will not turn off and reset unless you lock it up and come back about 20 minutes later, and it starts up perfectly. I have had it plugged in and it shows no fault codes, but who wants to be stuck in the middle of no where at 3 o'clock in the morning in a temporarily dead Freelander? Also does anyone know where you can get a parcel shelf for a 3 door Freelander??