faulty central locking?

I have an s reg 1.3 mk2 micra. the central locking has gone crazy since the cold weather. It locks and unlocks itself about 6 times before you can get in. it then locks itself a little while later and then repeats the process when you want to get out. The interior light also remains on all the time even though the switch is set to the right position. does anyone know of a fix?