Update : I removed the under panel and inspected the motor, its rusting in there, I think the spoiler must be leaking. The boot lid itself is rusting through EEK!

But, I applied some WD40 to the spoiler mechanism and motor, and then tightened up the bolts that hold the motor in place (one had a quarter inch play in it). After doing this I was delighted to notice my spoiler is working ok now

So, thanks for excellent advice peeps.

Now I need to sort those fogs and waterproof (then rust treat/proof) the boot lid. Is there a how-to?

Thanks