Post #13.

Ignoring the help you're getting is likely to mean you make your life harder.

 

Since you purchased the 2007 XJ8 only a few weeks ago, it wouldn't hurt at all to check the earth grounds inside the trunk (boot). Also make sure that both connections to the battery are clean and snug. Remember, you are dealing with relatively low voltages here, and the electronics inside the vehicle don't work well with loose or tarnished connections. No, not at all.