Barry
Jaguars are battery thirsty (especially I find my S-Type was).
I cured the problem by investing in a CTEK MS 7 Battery Charger / Re-conditioner . Use mine at least once per month and for at least 24 hours at a time. Marvellous machine which I use successfully Summer and Winter. Many people on this Forum find it a worthwhile investment for keeping a good battery in excellent condition.
Best Wishes and Regards, John