Thanks guys I am getting my brother in law who works for an auto electrical company to check out battery tomorrow, hope its the battery that's needs replacing which will be an ok result!

Have a 2003 x5 3.0 diesel sport M57 89k, regularly maintained by local BMW dealer. Over last few months the "trans fail safe message has been appearing and car slows and then comes to stand still, will then restart but unless the key is removed, error message still stays on. Interesting thing is ...