Amazon have 22% of the home entertainment market in the UK

"The online retailer overtook [HMV] in the run up to Christmas last year, making it the biggest seller of CDs, DVDs and video games in the UK, with a 22.4% market share. HMV is still in second place with 17.5%, putting it ahead of other mail-order sites, download stores and the supermarkets, though, of course, its costs – having to operate 200+ high street stores selling just entertainment product – are so much higher.
These figures come from research company Kantar Worldpanel, whose Consumer Insight Director Fiona Keenan, says: “Amazon’s strong performance is down to a number of factors: it is typically really competitive on price, has a wide range of products with no restriction on display space, and is known for its very good customer service”.
After HMV and Amazon come: Tesco (11.4%), Asda (8.1%), Game (7.7%), Sainsbury’s (5.2%), Play.com (4.9%), iTunes (3%) and Morrisons has (2.7%)."

Source:  CMU 8th February 2012