I order all the time from Zavvi.
Yes, they are extremely slow, but sometimes they've nice promotions.
I bought the Jurassic Park Limited Edition with the figure for only 20 Euro's (16 gpb), I believe its like 50 or 60 gbp on Amazon, but I could be wrong. Well, I thought that was a nice price and I received it within 10 days

.
But sometimes it takes months till my items arrive.
I ordered ''The Texas Chainsaw Massacre'' like 3 months ago and its still not shipped

. Zavvi is constantly sending me e-mails in which they tell me that they've to get the item from the supplier and that they apologize for the inconvenience caused. Well, I won't cancel the order. I'll only have to pay if they ship the product and it was only 4 or 5 gbp for the blu-ray, so what the hell.