Was easy in the end - I knew it would be. Attached battery charger and the alarm went off, then put the remote key in the ignition and hey-presto the alarm is silenced. Battery is now charging - I hope it's not knack'd, we'll see. Serves me right for being in hospital !
Ok, as NSC has the answer to everything, I have a silly car issue.
I was in hospital for a while and while I was in, my car battery went flat - not enough charge to open the doors with the remote key. I can unlock the doors with the manual key and open the bonnet. When I connect the battery...