I did shop in an HMV which is right across from my college..until I found a store called "That's Entertainment!" just down the road from it which sells used CDs and DVDs for 1.99! Maybe I'm just a cheap student, but the items always work perfectly (They can't sell them otherwise) so I don't mind it being used, especially at 1.99. I still buy new releases that I want from HMV though.
I was in a shop similar to this recently, I can't remember the name but "That's Entertainment" rings a bell... Anyway, I much prefer shopping in there to HMV. It's exactly as you say, at such low prices it doesn't matter if it's second hand or not. I'd rather buy a second hand dvd at a much lower price than pay at least twice as much for basically just plastic packaging.
If it works, of course.
EDIT- just looked it up. That's Entertainment has lots of stores in the UK, I'm surprised there aren't more as it is a fantastic idea for saving money and selling your own old dvds etc. They're also still doing free delivery if you order online which makes it more favourable than Amazon too!