Went out to the Lex this morning, turned the ignition on,Zilch Battery was dead as a dodo. Rang round for a battery,found an Exide for £45.
Asked the chap in the shop if he could recommend a way to change batteries without losing the radio codes, asked me if I had a power pack, as luck would have it I have, so plugged it into the cigar lighter,before disconnecting battery,changed batteries,and voila,he was right.
Just thought I would share this tip with you