As a shopper, I think it's immoral and I try to avoid buying from businesses who avoid tax in this way. However, if you're trying to compete against it, you're coming up against two huge barriers: knowledge and convenience. Just because corporation tax has been in the news a bit, doesn't mean that most people are aware of which businesses are dodging tax.
And convenience, in that it's very easy to keep shopping the way you usually do and quietly ignore the tax issue.
I would *love* companies to advertise how much tax they pay, and what % of revenue this represents.