Did the same thing myself a few years ago. Typed Natiionwide.co.uk (note the extra i) and found myself on something that looked a bit like what I was expecting but not quite the same. Fortunately I realised immediately and got out PDQ.... typed in what I thought was my bank name, but must have typed a letter incorrectly and ended up on a copycat site which was pretty much identical to my bank...
http://whois.domaintools.com/sanlander.co.uk
Well, I use Kaspersky Pure 3 on our 3 computers, they got this nice feature where you once enter your banking website or Paypal in the "secure banking" moduel, it then is verified. Whenever I want to do some banking I click on the link inside the Kaspersky program, and it opens up a secure window (has also a green colour edge around the whole window to show it's active). No chance of phishing there...