Zavvi's 9.99 shipping cost to India (7.99 most of the parts in the world) actually does not justify as parcels essentially reach after 3 weeks at least (to India at least). Tracking is there, which is not that proper from what I have observed from my past orders. So if you are ordering single steelbook, This does not justify at all.
But on other side, If you are ordering multiple steelbooks, lets say 5-6, and even with all different release dates, zavvi works out cheaper, as shipping cost remains same regardless of number of items in your order.
Amazon UK removes VAT for international orders, so item becomes cheaper at that time itself. Normal shipping cost is pretty good as well. And With many of my orders, I have received items in flat 3 business days by normal shipping method to India. Yes, 3 business days.
Finally it all depends upon packing material, and in that area both amazon and zavvi are progressing. Both are using special packing materials for delivering steelbooks. So that's good sign.
Certain risks like parcels, getting stuck with customs, damaged or lost are always there with international delivery. That we need to consider always.