Slim and save (vlcd) & caffine

[blibblibs]

I'm hoping someone who knows more about these things will be able to help.
I started this diet yesterday and the bumf says to avoid caffine in the first week to make sure you go into ketosis.
But I am really really struggling with the lack of coffee. The hunger I can deal with but the coffee is another level of hell. I haven't managed a day yet without, although it is only day two.
I've managed to cut it down from about 10cups to 4 but how much will this interfere with the diet? I take it black with no sugar so it's not the calories I'm worried about more the effect the caffine has.
Any advice would be appreciated as if it's a deal breaker I may need to rethink the whole thing!