As others have said, the problem is likely to be with your boots or shoes rather than your socks. I do a lot of walking and never get blisters... except, that is, when I wear a certain pair of boots. Although they feel comfortable, I start to get blisters after about 5 miles. They were no better after four attempts, so I stopped trying!
Again like others, most of my socks are Bridgedales and I recommend them highly. However, my favourite pair of socks are Smartwool. They were my first 'proper' walking socks (not counting quite a few pairs from Mountain Warehouse). I bought them from Cotswold Outdoor when I'd just been given brand new Salomon boots after arriving in my not-very-old squelching ones. I was so pleased with the no-quibble service that I went along with the assistant's advice to get some decent socks while I was there - and he recommended Smartwool. Until then, I wouldn't have dreamed of spending over £20 on a pair of socks!
Regarding Mountain Warehouse... I'm a big fan of some of their stuff, but not their socks. They're cheap and the ones I've had have felt fine, but they've developed holes far too quickly.