Sleek is sold on amazon.co.uk as well as in Superdrug stores. For the last few months the Sleek stands in the 3 Superdrugs nearby me have always been hideous - hideously messy and caked in what looks like visible germs and always out of stock of everything I want. So I decided amazon was a safer bet.
Colourwise these are pretty dark for what they are named.
I got the Light Kit in Creme to Powder foundation and I ended up being between Shell and Sand. I'd say I'm medium/fair toned (NW20/NC25) so I was surprised to find myself between the lightest two shades available. I would have called this the Medium Kit myself.
Texture wise these were very creamy as the name implies and very blendable. I didn't think the coverage was very good as it didn't cover the redness I have around my nose. I felt I had to apply a lot of product to get the coverage I wanted and it took some time to do so. For myself I prefer liquid foundation but I would still use these on others who don't have too many imperfections as it did leave a nice, powder finish. I wouldn't recommend it to those with dry skin as I think it would stick to dry patches.
And I got the Light/Medium in New Skin Revive and these were a lot darker:
I wouldn't recommend any of these foundations for the super pale or those with neutral or pink undertones as most of these shades have yellow undertones (some were even borderline orange).
I liked the formula of the New Skin Revive better as I prefer liquid foundation. Coverage was okay (medium). Nice natural finish (wasn't too matte or dewy). I can't really give an in depth review, however, as I didn't wear these foundations for long (since they were like 5 shades too dark for me).
These testers are also available in Medium Dark and Dark.
I paid £2.99 for each set from amazon but they are also available on the Sleek website.