Lights on alarm stopped working ?

Hi all .

I have a 57 Roomster which has been with out a doubt the best car i have owned to date .

The first thing has just gone wrong !!

Its the warning chime to tell you that you have left your lights on when you remove the iginition key !

It stopped working a few days ago, any ideas ? hopefully just a fuse but not had any time off in daylight yet (shift work) to have a look ?

Thanks

Skipp