I'm also a victim of the 70s and as I have got older I have so many white hairs in my eyebrows. These seem very fragile and, when taking off my eye makeup they come away on my cotton wool pad! Hence I have very few!
I love Yves St Laurent eye pencil and the one I use is a soft, grey/brown, perfect for faded blonde/grey/brown. I can't tell you the number as I'm almost through it, but it will be easily found on the counter.
I've also bought the Benefit eyebrow palette; this is brilliant when you have a little more time to spend on your 'slap'.
I am going to try the 'Wunderbrow', which I understand is stocked by Boots.
I won't buy online until I've tried this out so I'm hoping that I can get this in Boots.