Zavvi Bargain Codes
Zavvi Vouchers: Zavvi Discount Codes, Voucher Codes & Promotional Codes for DVDs, Blu-ray Movies & Games
I just checked the £4 off £40 or more voucher - it works.
I also then checked the 10% off on the same item, and it knocked me 10% off it.
So it looks like both codes are working, but hurry, they're only valid til April 10th.