aluminium door skins without winding windows will save quite a bit,
Using non-servo brakes
rear beam conversion
half size battery
smaller alternator
cutting unwanted metal out (rear seat base and bins)
You can have two of cheap, light, or comfortable. But not all three.
See Force Racing, specialist components and KAD for lovely shiney bits that also save weight. (i.e. 10" SC wheels will save nearly 2kg per wheel over 12" minilights, and even more over sports pack wheels etc)