When searching for a keyword, it receives 420 UK searches, a very targeted niche. No adverts have ever appeared on the results, yet the competition is medium. I set a bid and the traffic estimate is 0. Whats all this about.
Are you sure there are no as in the UK? If you're not in the UK, just going to google.co.uk won't be enough. Use the Google Ad Preview Tool within adwords to see the real picture.
Don't worry about traffic estimator tool. Because it depends on history. Just go with keyword and run your ad. You will get batter idea about that. thank you.