Paddyanne, I know they are all available on QVC, but they are usually full price. They items I like are rarely discounted.
I'm signed up to all sites you mention and am often offered discount codes, I rarely pay full price, obtaining free delivery.
I watch QVC fashion hours, spot something I like, then look for it elsewhere at a cheaper price
Recently I bought a top from the Joules outlet, with free delivery, then saw it on QVC for almost double, plus delivery.
However, I've been with QVC from the beginning, avail myself of the TSVs, but have yet to be offered a discount voucher from them for any items.
Today I received the le Creuset TSV, at half price. I checked the price against other sites, before I bought it. That was unusual for QVC.