I thought I would just share with you my trouble with an apparently simple job like changing a battery on my S Type. I disconnected the battery terminals no trouble but when I tried to unscrew the long bolt in the boot floor to remove the securing bracket, It wouidn't budge. After several applications of WD40 and much scratching of head I discovered that the bolt which has an unnecessarily long threaded portion, goes straight through the boot floor and the end is exposed to the elements under the car. After identifying which was the right bolt, I was able to wire brush it and spray WD40 from both sides. Eventually after about 30 minutes the bolt finally came free. To assist next time I applied plenty of grease to the threads. If anyone is contemplating changing their battery Then I would recommend giving the bolt a good spraying a few days in advance.The bolt in question is the middle one of 3 that runs longwise up the boot floor.