Thank you both for the replies. I will see how I get on over the coming days and hopefully the MPG will lift to 30 on average as that is what I was hoping for. None the less, its still a lovely, lovely car (or suv) and is very comfortable.
I remember watching Harry's Garage on Youtube (the former EVO magazine owner) and he had one of those solar devices on his SL600 in Nice which kept a charge going to the battery. After a few months left in a car park, he unlocks the car and it starts right away! Now, just need some more sunshine... !
Thanks