Silver

I would say follow all of your usual methods for achieving white hair (great tutorial by the way, thank you) at first. 

I really hope this works better for you or anyone else that tries it, but Directions Silver didn't seem to alter my hair in the slightest.  I tried it at varying times on various conditions of my hair (towel-dried, dry, clarified, 45 min, 2 hrs....).  Perhaps if you get hair to the 'white' condition base it would do well, however. 

What does work beautifully is Wella's Color Charm 'Light Drabber.'  The thing about this one, however, is that it comes out a strong blue-violet at first. 

This is after 3 washes

At 6, it's perfect

After that it still looked great for about 4-5 days, and the washes in between the violety-color and perfect were a darker silver. 
I'm sure you could keep this looking good for longer with a toner (Wella Silver Lady?) but I didn't do it with mine. 

Oh, sorry and this was the starting base blonde; natural dark blonde lightened 2x.  I don't know the volume, had it done at my hairdressers since the color before was patchy on the ends from a previous lift.

my matey sam sam, whi is currently going from virgin dark brown to silver (on dreads) is using a shampoo that sounds amazing...im just waiting for her to text back, then i'll tell thee. i think it's a pit pricey, but it sounds amazing to be honeset!

devilnevercries, its for a friend, shall i get his hair to a whiteblonde first, then use the Wella's Color Charm 'Light Drabber. then tone it after with "Wella Silver lady?"

http://www.bona-hair.com/true_silver_shampoo.htm

this is the stuff =) i shall be using it once the blue is gone

Oohh cool! ill have to look up where to get some of that stuff, are you going Silver next Pippa?

yes indeedy =) sam sam is my trial and error person =)

OOoo lush, when dya think you'll do it? =]

may/june. goona let the blue fade, hopefully get some dread at some point in the near future, failing that, im gonna let it fade, then thinking about colour b4 as im white blonde under the blue, then bleach baths until all the blue is gone =) i've been k-paking and deep conditioning like a ninja in prepration

devilnevercries, its for a friend, shall i get his hair to a whiteblonde first, then use the Wella's Color Charm 'Light Drabber. then tone it after with "Wella Silver lady?"

I'd probably tone it first to neutralize any of the leftover yellows~ you could also use the toner later on to keep it lookin nice and silver; the color would probably last longer.  Wella toners are pretty gentle on my hair wheras the semi (Light Drabber) kind of damaged it; so be careful that their hair is in good condition too.  I would probably not let it process for more than 40 minutes max for this reason; I'd left mine on 45 minutes.   

Good luck!  I hope this cuts through some of the horrible 'figuring out stuff' trial-and-error that usually goes with silver hair....@_@  haha I spent way too much money arriving at this solution. 

And the silver shampoos are cool, they do help when it starts to fade~

awesome, thanks devilnevercries, i shall post some pics of the finished result =)

and pippa if u come to cornwall over the summer ill brade ur dreads in if u like =)

thank you sweetie =) may ned up taking you up on that offer =) or you can just make me a cuppa. im aiming to get down and see your pretty face

Ah, nice!  I'd like to see how it turns out.  Thank you. 

Also, it seems to me from the posts you've done that you're in cosmetology school?  Or no?  I'm about to start here in the states and was just curious what it's like in the UK.