1 - Theres better alternatives than sci-mx, cheaper ones too. Take a look at Nutrisport 90+ and boditroics.
2- A protein shake post-workout is to help in recovery, so yes 30-45minutes after a workout would be ideal, but if missed by 10-20minutes is not really going to make thatt much of a difference.
3- As you're a self professed noobie i wouldnt try creatine yet but if you're keen to give it ago i would first read up on it, and what it does before jumping straight in. See - http://www.muscletalk.co.uk/article-creatine.aspx
4- Pretty much, if not all protein shakes, can be taking with either milk or water, so theres not really a problem there. Many just use milk to add cals and more protein to their shake, and some just prefere the taste of a thicker shake(with milk) than a thinner one with water.
5- I myself havn't used discount-supplements.co.uk but many have on here. I personally can vouch for myprotein.co.uk and bodybuildingwarehouse.co.uk both with great customer service and fast delivery, with the latter if adding in some extras which ive always said i liked (:
Quite a long winded post but hope it helps buddy.