Thanks for all the great posts guys, I have been attentively following this thread for several days now and it has finally prompted me to sign up to the forums!
I did an unboxing video today of the Metal Gear Solid: HD Collection Limited Edition (PlayStation 3, Zavvi.com Exclusive) and can confirm that it is indeed a steelbook. I can also confirm that Zavvi packaged it poorly and the outter cardboard box of the Limited Edition is really thin and cheap (mine had two crushed corners) - thankfully the contents inside were in pristine condition. (I was offered an exchange but had zero faith the replacement would arrive in better condition - I therefore cut my losses and accepted their offer of a 10% refund).
Metal Gear Solid: HD Collection Limited Edition Unboxing (PlayStation 3, Zavvi.com Exclusive) - Alternative Magazine Online