After reconnecting the battery the radio failed because of wrong code.
Left power and radio on for two hours and got 'add code' again on screen. Put in the right code but radio went in security again. No luck anymore after another two hours.
Since then (4 months ago) radio is constant on security and 'add code' never shows up anymore.
Who knows a solution other than finding another radio? Thanks

Few years back I did the same as you, disconected the battery and on reconnection, the radio demanded a code. I put in the wrong one and the radio went into sulk mode. I left it switched on and after half an hour it came to life; worked fine. By then I'd found the bit of paper with the code on it; subsequently it accepted the code ok.

What might have happened with yours is it defaulted to factory setting; usually something basic like 0000 or 1234 so the 'right' code won't work. If you get it working using the factory setting, somewhere in the book there should be a way of resetting the number to whatever you like.

Sometimes leaving the radio fully disconnected (including the permanent 1+) for a few days then re-connecting everything works; it powers up and asks for a code. Alternatively, I've read that putting the radio in a freezer overnight can bring it out of 'security' but I've never tried this; maybe it's just an internet story.

Just a thought; if you decide to replace it, leave whatever you replace it with loose and easy to remove. Better to lose a radio than have someone wreck the dashboard trying to prise it out.

Sadly the same thing happened to me on our mk 1 a couple of years ago, I tried everything including putting it in the freezer. Nothing worked I finished up buying a second hand XM radio. The problem is there not so many broked XM around now.